@overfullrule=0pt
GNU Emacs Manual
Sixth Edition, Emacs Version 18
for Unix Users
February 1988 (General Public License upgraded, January 1991)
Richard Stallman Copyright (C) 1985, 1986, 1988 Richard M. Stallman.
Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.
Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the sections entitled "The GNU Manifesto", "Distribution" and "GNU General Public License" are included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.
Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the sections entitled "The GNU Manifesto", "Distribution" and "GNU General Public License" may be included in a translation approved by the author instead of in the original English.
This manual documents the use and simple customization of the Emacs editor. The reader is not expected to be a programmer. Even simple customizations do not require programming skill, but the user who is not interested in customizing can ignore the scattered customization hints.
This is primarily a reference manual, but can also be used as a primer. However, I recommend that the newcomer first use the on-line, learn-by-doing tutorial, which you get by running Emacs and typing C-h t. With it, you learn Emacs by using Emacs on a specially designed file which describes commands, tells you when to try them, and then explains the results you see. This gives a more vivid introduction than a printed manual.
On first reading, just skim chapters one and two, which describe the notational conventions of the manual and the general appearance of the Emacs display screen. Note which questions are answered in these chapters, so you can refer back later. After reading chapter four you should practice the commands there. The next few chapters describe fundamental techniques and concepts that are used constantly. You need to understand them thoroughly, experimenting with them if necessary.
To find the documentation on a particular command, look in the index. Keys (character commands) and command names have separate indexes. There is also a glossary, with a cross reference for each term.
This manual comes in two forms: the published form and the Info form. The Info form is for on-line perusal with the INFO program; it is distributed along with GNU Emacs. Both forms contain substantially the same text and are generated from a common source file, which is also distributed along with GNU Emacs.
GNU Emacs is a member of the Emacs editor family. There are many Emacs editors, all sharing common principles of organization. For information on the underlying philosophy of Emacs and the lessons learned from its development, write for a copy of AI memo 519a, "Emacs, the Extensible, Customizable Self-Documenting Display Editor", to Publications Department, Artificial Intelligence Lab, 545 Tech Square, Cambridge, MA 02139, USA. At last report they charge $2.25 per copy. Another useful publication is LCS TM-165, "A Cookbook for an Emacs", by Craig Finseth, available from Publications Department, Laboratory for Computer Science, 545 Tech Square, Cambridge, MA 02139, USA. The price today is $3.
This edition of the manual is intended for use with GNU Emacs installed on Unix systems. GNU Emacs can also be used on VMS systems, which have different file name syntax and do not support all GNU Emacs features. A VMS edition of this manual may appear in the future.
GNU Emacs is free; this means that everyone is free to use it and free to redistribute it on a free basis. GNU Emacs is not in the public domain; it is copyrighted and there are restrictions on its distribution, but these restrictions are designed to permit everything that a good cooperating citizen would want to do. What is not allowed is to try to prevent others from further sharing any version of GNU Emacs that they might get from you. The precise conditions are found in the GNU General Public License that comes with Emacs and also appears following this section.
The easiest way to get a copy of GNU Emacs is from someone else who has it. You need not ask for permission to do so, or tell any one else; just copy it.
If you have access to the Internet, you can get the latest distribution version of GNU Emacs from host `prep.ai.mit.edu' using anonymous login. See the file `/u2/emacs/GETTING.GNU.SOFTWARE' on that host to find out about your options for copying and which files to use.
You may also receive GNU Emacs when you buy a computer. Computer manufacturers are free to distribute copies on the same terms that apply to everyone else. These terms require them to give you the full sources, including whatever changes they may have made, and to permit you to redistribute the GNU Emacs received from them under the usual terms of the General Public License. In other words, the program must be free for you when you get it, not just free for the manufacturer.
If you cannot get a copy in any of those ways, you can order one from the Free Software Foundation. Though Emacs itself is free, our distribution service is not. An order form is included at the end of manuals printed by the Foundation. It is also included in the file `etc/DISTRIB' in the Emacs distribution. For further information, write to
Free Software Foundation 675 Mass Ave Cambridge, MA 02139 USA
The income from distribution fees goes to support the foundation's purpose: the development of more free software to distribute just like GNU Emacs.
If you find GNU Emacs useful, please send a donation to the Free Software Foundation. This will help support development of the rest of the GNU system, and other useful software beyond that. Your donation is tax deductible.
Copyright (C) 1989 Free Software Foundation, Inc. 675 Mass Ave, Cambridge, MA 02139, USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
The license agreements of most software companies try to keep users at the mercy of those companies. By contrast, our General Public License is intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users. The General Public License applies to the Free Software Foundation's software and to any other program whose authors commit to using it. You can use it for your programs, too.
When we speak of free software, we are referring to freedom, not price. Specifically, the General Public License is designed to make sure that you have the freedom to give away or sell copies of free software, that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.
To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.
For example, if you distribute copies of a such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must tell them their rights.
We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.
Also, for each author's protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors' reputations.
The precise terms and conditions for copying, distribution and modification follow.
NO WARRANTY
If you develop a new program, and you want it to be of the greatest possible use to humanity, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the "copyright" line and a pointer to where the full notice is found.
one line to give the program's name and a brief idea of what it does. Copyright (C) 19yy name of author This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 1, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
Also add information on how to contact you by electronic and paper mail.
If the program is interactive, make it output a short notice like this when it starts in an interactive mode:
Gnomovision version 69, Copyright (C) 19yy name of author Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. This is free software, and you are welcome to redistribute it under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than `show w' and `show c'; they could even be mouse-clicks or menu items--whatever suits your program.
You should also get your employer (if you work as a programmer) or your school, if any, to sign a "copyright disclaimer" for the program, if necessary. Here a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright interest in the program `Gnomovision' (a program to direct compilers to make passes at assemblers) written by James Hacker. signature of Ty Coon, 1 April 1989 Ty Coon, President of Vice
That's all there is to it!
You are reading about GNU Emacs, the GNU incarnation of the advanced, self-documenting, customizable, extensible real-time display editor Emacs. (The `G' in `GNU' is not silent.)
We say that Emacs is a display editor because normally the text being edited is visible on the screen and is updated automatically as you type your commands. See section The Organization of the Screen.
We call it a real-time editor because the display is updated very frequently, usually after each character or pair of characters you type. This minimizes the amount of information you must keep in your head as you edit. See section Basic Editing Commands.
We call Emacs advanced because it provides facilities that go beyond simple insertion and deletion: filling of text; automatic indentation of programs; viewing two or more files at once; and dealing in terms of characters, words, lines, sentences, paragraphs, and pages, as well as expressions and comments in several different programming languages. It is much easier to type one command meaning "go to the end of the paragraph" than to find that spot with simple cursor keys.
Self-documenting means that at any time you can type a special character, Control-h, to find out what your options are. You can also use it to find out what any command does, or to find all the commands that pertain to a topic. See section Help.
Customizable means that you can change the definitions of Emacs commands in little ways. For example, if you use a programming language in which comments start with `<**' and end with `**>', you can tell the Emacs comment manipulation commands to use those strings (see section Manipulating Comments). Another sort of customization is rearrangement of the command set. For example, if you prefer the four basic cursor motion commands (up, down, left and right) on keys in a diamond pattern on the keyboard, you can have it. See section Customization.
Extensible means that you can go beyond simple customization and write entirely new commands, programs in the Lisp language to be run by Emacs's own Lisp interpreter. Emacs is an "on-line extensible" system, which means that it is divided into many functions that call each other, any of which can be redefined in the middle of an editing session. Any part of Emacs can be replaced without making a separate copy of all of Emacs. Most of the editing commands of Emacs are written in Lisp already; the few exceptions could have been written in Lisp but are written in C for efficiency. Although only a programmer can write an extension, anybody can use it afterward.
Emacs divides the screen into several areas, each of which contains its own sorts of information. The biggest area, of course, is the one in which you usually see the text you are editing.
When you are using Emacs, the screen is divided into a number of windows. Initially there is one text window occupying all but the last line, plus the special echo area or minibuffer window in the last line. The text window can be subdivided horizontally or vertically into multiple text windows, each of which can be used for a different file (see section Multiple Windows). The window that the cursor is in is the selected window, in which editing takes place. The other windows are just for reference unless you select one of them.
Each text window's last line is a mode line which describes what is going on in that window. It is in inverse video if the terminal supports that, and contains text that starts like `-----Emacs: something'. Its purpose is to indicate what buffer is being displayed above it in the window; what major and minor modes are in use; and whether the buffer's text has been changed.
When Emacs is running, the terminal's cursor shows the location at which editing commands will take effect. This location is called point. Other commands move point through the text, so that you can edit at different places in it.
While the cursor appears to point at a character, point should be thought of as between two characters; it points before the character that the cursor appears on top of. Sometimes people speak of "the cursor" when they mean "point", or speak of commands that move point as "cursor motion" commands.
Terminals have only one cursor, and when output is in progress it must appear where the typing is being done. This does not mean that point is moving. It is only that Emacs has no way to show you the location of point except when the terminal is idle.
If you are editing several files in Emacs, each file has its own point location. A file that is not being displayed remembers where point is so that it can be seen when you look at that file again.
When there are multiple text windows, each window has its own point location. The cursor shows the location of point in the selected window. This also is how you can tell which window is selected. If the same buffer appears in more than one window, point can be moved in each window independently.
The term `point' comes from the character `.', which was the command in TECO (the language in which the original Emacs was written) for accessing the value now called `point'.
The line at the bottom of the screen (below the mode line) is the echo area. It is used to display small amounts of text for several purposes.
Echoing means printing out the characters that you type. Emacs never echoes single-character commands, and multi-character commands are echoed only if you pause while typing them. As soon as you pause for more than a second in the middle of a command, all the characters of the command so far are echoed. This is intended to prompt you for the rest of the command. Once echoing has started, the rest of the command is echoed immediately when you type it. This behavior is designed to give confident users fast response, while giving hesitant users maximum feedback. You can change this behavior by setting a variable (see section Variables Controlling Display).
If a command cannot be executed, it may print an error message in the echo area. Error messages are accompanied by a beep or by flashing the screen. Also, any input you have typed ahead is thrown away when an error happens.
Some commands print informative messages in the echo area. These messages look much like error messages, but they are not announced with a beep and do not throw away input. Sometimes the message tells you what the command has done, when this is not obvious from looking at the text being edited. Sometimes the sole purpose of a command is to print a message giving you specific information. For example, the command C-x = is used to print a message describing the character position of point in the text and its current column in the window. Commands that take a long time often display messages ending in `...' while they are working, and add `done' at the end when they are finished.
The echo area is also used to display the minibuffer, a window that is used for reading arguments to commands, such as the name of a file to be edited. When the minibuffer is in use, the echo area begins with a prompt string that usually ends with a colon; also, the cursor appears in that line because it is the selected window. You can always get out of the minibuffer by typing C-g. See section The Minibuffer.
Each text window's last line is a mode line which describes what is going on in that window. When there is only one text window, the mode line appears right above the echo area. The mode line is in inverse video if the terminal supports that, starts and ends with dashes, and contains text like `Emacs: something'.
If a mode line has something else in place of `Emacs: something', then the window above it is in a special subsystem such as Dired. The mode line then indicates the status of the subsystem.
Normally, the mode line has the following appearance:
--ch-Emacs: buf (major minor)----pos------
This gives information about the buffer being displayed in the window: the buffer's name, what major and minor modes are in use, whether the buffer's text has been changed, and how far down the buffer you are currently looking.
ch contains two stars `**' if the text in the buffer has been edited (the buffer is "modified"), or `--' if the buffer has not been edited. Exception: for a read-only buffer, it is `%%'.
buf is the name of the window's chosen buffer. The chosen buffer in the selected window (the window that the cursor is in) is also Emacs's selected buffer, the one that editing takes place in. When we speak of what some command does to "the buffer", we are talking about the currently selected buffer. See section Using Multiple Buffers.
pos tells you whether there is additional text above the top of the screen, or below the bottom. If your file is small and it is all on the screen, pos is `All'. Otherwise, it is `Top' if you are looking at the beginning of the file, `Bot' if you are looking at the end of the file, or `nn%', where nn is the percentage of the file above the top of the screen.
major is the name of the major mode in effect in the buffer. At any time, each buffer is in one and only one of the possible major modes. The major modes available include Fundamental mode (the least specialized), Text mode, Lisp mode, and C mode. See section Major Modes, for details of how the modes differ and how to select one.
minor is a list of some of the minor modes that are turned on at the moment in the window's chosen buffer. `Fill' means that Auto Fill mode is on. `Abbrev' means that Word Abbrev mode is on. `Ovwrt' means that Overwrite mode is on. See section Minor Modes, for more information. `Narrow' means that the buffer being displayed has editing restricted to only a portion of its text. This is not really a minor mode, but is like one. See section Narrowing. `Def' means that a keyboard macro is being defined. See section Keyboard Macros.
Some buffers display additional information after the minor modes. For example, Rmail buffers display the current message number and the total number of messages. Compilation buffers and Shell mode display the status of the subprocess.
In addition, if Emacs is currently inside a recursive editing level, square brackets (`[...]') appear around the parentheses that surround the modes. If Emacs is in one recursive editing level within another, double square brackets appear, and so on. Since this information pertains to Emacs in general and not to any one buffer, the square brackets appear in every mode line on the screen or not in any of them. See section Recursive Editing Levels.
Emacs can optionally display the time and system load in all mode lines. To enable this feature, type M-x display-time. The information added to the mode line usually appears after the file name, before the mode names and their parentheses. It looks like this:
hh:mmpm l.ll [d]
(Some fields may be missing if your operating system cannot support them.) hh and mm are the hour and minute, followed always by `am' or `pm'. l.ll is the average number of running processes in the whole system recently. d is an approximate index of the ratio of disk activity to cpu activity for all users.
The word `Mail' appears after the load level if there is mail for you that you have not read yet.
Customization note: the variable mode-line-inverse-video controls
whether the mode line is displayed in inverse video (assuming the terminal
supports it); nil means no inverse video. The default is t.
This chapter explains the character set used by Emacs for input commands and for the contents of files, and also explains the concepts of keys and commands which are necessary for understanding how your keyboard input is understood by Emacs.
GNU Emacs uses the ASCII character set, which defines 128 different character codes. Some of these codes are assigned graphic symbols such as `a' and `='; the rest are control characters, such as Control-a (also called C-a for short). C-a gets its name from the fact that you type it by holding down the CTRL key and then pressing a. There is no distinction between C-a and C-A; they are the same character.
Some control characters have special names, and special keys you can type them with: RET, TAB, LFD, DEL and ESC. The space character is usually referred to below as SPC, even though strictly speaking it is a graphic character whose graphic happens to be blank.
Emacs extends the 7-bit ASCII code to an 8-bit code by adding an extra bit to each character. This makes 256 possible command characters. The additional bit is called Meta. Any ASCII character can be made Meta; examples of Meta characters include Meta-a (M-a, for short), M-A (not the same character as M-a, but those two characters normally have the same meaning in Emacs), M-RET, and M-C-a. For traditional reasons, M-C-a is usually called C-M-a; logically speaking, the order in which the modifier keys CTRL and META are mentioned does not matter.
Some terminals have a META key, and allow you to type Meta characters by holding this key down. Thus, Meta-a is typed by holding down META and pressing a. The META key works much like the SHIFT key. Such a key is not always labeled META, however, as this function is often a special option for a key with some other primary purpose.
If there is no META key, you can still type Meta characters using two-character sequences starting with ESC. Thus, to enter M-a, you could type ESC a. To enter C-M-a, you would type ESC C-a. ESC is allowed on terminals with Meta keys, too, in case you have formed a habit of using it.
Emacs believes the terminal has a META key if the variable
meta-flag is non-nil. Normally this is set automatically
according to the termcap entry for your terminal type. However, sometimes
the termcap entry is wrong, and then it is useful to set this variable
yourself. See section Variables, for how to do this.
Emacs buffers also use an 8-bit character set, because bytes have 8 bits, but only the ASCII characters are considered meaningful. ASCII graphic characters in Emacs buffers are displayed with their graphics. LFD is the same as a newline character; it is displayed by starting a new line. TAB is displayed by moving to the next tab stop column (usually every 8 columns). Other control characters are displayed as a caret (`^') followed by the non-control version of the character; thus, C-a is displayed as `^A'. Non-ASCII characters 128 and up are displayed with octal escape sequences; thus, character code 243 (octal), also called M-# when used as an input character, is displayed as `\243'.
A complete key---where `key' is short for key sequence---is a sequence of keystrokes that are understood by Emacs as a unit, as a single command (possibly undefined). Most single characters constitute complete keys in the standard Emacs command set; there are also some multi-character keys. Examples of complete keys are C-a, X, RET, C-x C-f and C-x 4 C-f.
A prefix key is a sequence of keystrokes that are the beginning of a complete key, but not a whole one. Prefix keys and complete keys are collectively called keys.
A prefix key is the beginning of a series of longer sequences that are valid keys; adding any single character to the end of the prefix gives a valid key, which could be defined as an Emacs command, or could be a prefix itself. For example, C-x is standardly defined as a prefix, so C-x and the next input character combine to make a two-character key. There are 256 different two-character keys starting with C-x, one for each possible second character. Many of these two-character keys starting with C-x are standardly defined as Emacs commands. Notable examples include C-x C-f and C-x s (see section File Handling).
Adding one character to a prefix key does not have to form a complete key. It could make another, longer prefix. For example, C-x 4 is itself a prefix that leads to 256 different three-character keys, including C-x 4 f, C-x 4 b and so on. It would be possible to define one of those three-character sequences as a prefix, creating a series of four-character keys, but we did not define any of them this way.
By contrast, the two-character sequence C-f C-k is not a key, because the C-f is a complete key in itself. It's impossible to give C-f C-k an independent meaning as a command as long as C-f retains its meaning. C-f C-k is two commands.
All told, the prefix keys in Emacs are C-c, C-x, C-h, C-x 4, and ESC. But this is not built in; it is just a matter of Emacs's standard key bindings. In customizing Emacs, you could make new prefix keys, or eliminate these. See section Customizing Key Bindings.
Whether a sequence is a key can be changed by customization. For example, if you redefine C-f as a prefix, C-f C-k automatically becomes a key (complete, unless you define it too as a prefix). Conversely, if you remove the prefix definition of C-x 4, then C-x 4 f (or C-x 4 anything) is no longer a key.
This manual is full of passages that tell you what particular keys do. But Emacs does not assign meanings to keys directly. Instead, Emacs assigns meanings to functions, and then gives keys their meanings by binding them to functions.
A function is a Lisp object that can be executed as a program. Usually
it is a Lisp symbol which has been given a function definition; every
symbol has a name, usually made of a few English words separated by dashes,
such as next-line or forward-word. It also has a
definition which is a Lisp program; this is what makes the function
do what it does. Only some functions can be the bindings of keys; these
are functions whose definitions use interactive to specify how to
call them interactively. Such functions are called commands, and
their names are command names. More information on this subject will
appear in the GNU Emacs Lisp Manual (which is not yet written).
The bindings between keys and functions are recorded in various tables called keymaps. See section Keymaps.
When we say that "C-n moves down vertically one line" we are
glossing over a distinction that is irrelevant in ordinary use but is vital
in understanding how to customize Emacs. It is the function
next-line that is programmed to move down vertically. C-n has
this effect because it is bound to that function. If you rebind
C-n to the function forward-word then C-n will move
forward by words instead. Rebinding keys is a common method of
customization.
In the rest of this manual, we usually ignore this subtlety to keep
things simple. To give the customizer the information he needs, we
state the name of the command which really does the work in parentheses
after mentioning the key that runs it. For example, we will say that
"The command C-n (next-line) moves point vertically down,"
meaning that next-line is a command that moves vertically down
and C-n is a key that is standardly bound to it.
While we are on the subject of information for customization only, it's a
good time to tell you about variables. Often the description of a
command will say, "To change this, set the variable mumble-foo."
A variable is a name used to remember a value. Most of the variables
documented in this manual exist just to facilitate customization: some
command or other part of Emacs examines the variable and behaves
differently accordingly. Until you are interested in customizing, you can
ignore the information about variables. When you are ready to be
interested, read the basic information on variables, and then the
information on individual variables will make sense. See section Variables.
The usual way to invoke Emacs is just to type emacs RET at the shell. Emacs clears the screen and then displays an initial advisor message and copyright notice. You can begin typing Emacs commands immediately afterward.
Some operating systems insist on discarding all type-ahead when Emacs starts up; they give Emacs no way to prevent this. Therefore, it is wise to wait until Emacs clears the screen before typing your first editing command.
Before Emacs reads the first command, you have not had a chance to give a
command to specify a file to edit. But Emacs must always have a current
buffer for editing. In an attempt to do something useful, Emacs presents a
buffer named `*scratch*' which is in Lisp Interaction mode; you can
use it to type Lisp expressions and evaluate them, or you can ignore that
capability and simply doodle. (You can specify a different major mode for
this buffer by setting the variable initial-major-mode in your init
file. See section The Init File, .emacs.)
It is also possible to specify files to be visited, Lisp files to be loaded, and functions to be called, by giving Emacs arguments in the shell command line. See section Command Line Switches and Arguments.
There are two commands for exiting Emacs because there are two kinds of exiting: suspending Emacs and killing Emacs. Suspending means stopping Emacs temporarily and returning control to its superior (usually the shell), allowing you to resume editing later in the same Emacs job, with the same files, same kill ring, same undo history, and so on. This is the usual way to exit. Killing Emacs means destroying the Emacs job. You can run Emacs again later, but you will get a fresh Emacs; there is no way to resume the same editing session after it has been killed.
suspend-emacs).
save-buffers-kill-emacs).
To suspend Emacs, type C-z (suspend-emacs). This takes
you back to the shell from which you invoked Emacs. You can resume
Emacs with the command %emacs if you are using the C shell.
On systems that do not permit programs to be suspended, C-z runs an
inferior shell that communicates directly with the terminal, and Emacs
waits until you exit the subshell. The only way on these systems to get
back to the shell from which Emacs was run (to log out, for example) is to
kill Emacs. C-d or exit are typical commands to exit a
subshell.
To kill Emacs, type C-x C-c (save-buffers-kill-emacs). A
two-character key is used for this to make it harder to type. Unless a
numeric argument is used, this command first offers to save any modified
buffers. If you do not save them all, it asks for reconfirmation with
yes before killing Emacs, since any changes not saved before that will be
lost forever. Also, if any subprocesses are still running, C-x C-c
asks for confirmation about them, since killing Emacs will kill the
subprocesses immediately.
In most programs running on Unix, certain characters may instantly suspend or kill the program. (In Berkeley Unix these characters are normally C-z and C-c.) This Unix feature is turned off while you are in Emacs. The meanings of C-z and C-x C-c as keys in Emacs were inspired by the standard Berkeley Unix meanings of C-z and C-c, but that is their only relationship with Unix. You could customize these keys to do anything (see section Keymaps).
GNU Emacs supports command line arguments to request various actions when invoking Emacs. These are for compatibility with other editors and for sophisticated activities. They are not needed for ordinary editing with Emacs, so new users can skip this section.
You may be used to using command line arguments with other editors to specify which file to edit. That's because many other editors are designed to be started afresh each time you want to edit. You edit one file and then exit the editor. The next time you want to edit either another file or the same one, you must run the editor again. With these editors, it makes sense to use a command line argument to say which file to edit.
The recommended way to use GNU Emacs is to start it only once, just after you log in, and do all your editing in the same Emacs process. Each time you want to edit a different file, you visit it with the existing Emacs, which eventually comes to have many files in it ready for editing. Usually you do not kill the Emacs until you are about to log out.
When files are nearly always read by typing commands to an editor that is already running, command line arguments for specifying a file when the editor is started are seldom needed.
Emacs accepts command-line arguments that specify files to visit, functions to call, and other activities and operating modes.
The command arguments are processed in the order they appear in the command argument list; however, certain arguments (the ones in the second table) must be at the front of the list if they are used.
Here are the arguments allowed:
find-file. See section Visiting Files.
find-file, then go to line number
linenum in it.
load.
See section Libraries of Lisp Code for Emacs.
The remaining switches are recognized only at the beginning of the command line. If more than one of them appears, they must appear in the order that they appear in this table.
stdout only what would normally be printed in the echo
area under program control.
Batch mode is used for running programs written in Emacs Lisp from
shell scripts, makefiles, and so on. Normally the `-l' switch
or `-f' switch will be used as well, to invoke a Lisp program
to do the batch processing.
`-batch' implies `-q' (do not load an init file). It also causes
Emacs to kill itself after all command switches have been processed. In
addition, auto-saving is not done except in buffers for which it has been
explicitly requested.
Note that the init file can get access to the command line argument
values as the elements of a list in the variable command-line-args.
(The arguments in the second table above will already have been processed
and will not be in the list.) The init file can override the normal
processing of the other arguments by setting this variable.
One way to use command switches is to visit many files automatically:
emacs *.c
passes each .c file as a separate argument to Emacs, so that Emacs
visits each file (see section Visiting Files).
Here is an advanced example that assumes you have a Lisp program file called `hack-c-program.el' which, when loaded, performs some useful operation on current buffer, expected to be a C program.
emacs -batch foo.c -l hack-c-program -f save-buffer -kill > log
Here Emacs is told to visit `foo.c', load `hack-c-program.el'
(which makes changes in the visited file), save `foo.c' (note that
save-buffer is the function that C-x C-s is bound to), and
then exit to the shell that this command was done with. `-batch'
guarantees there will be no problem redirecting output to `log',
because Emacs will not assume that it has a display terminal to work with.
We now give the basics of how to enter text, make corrections, and
save the text in a file. If this material is new to you, you might
learn it more easily by running the Emacs learn-by-doing tutorial. To
do this, type Control-h t (help-with-tutorial).
To insert printing characters into the text you are editing, just type them. This inserts the character into the buffer at the cursor (that is, at point; see section Point). The cursor moves forward. Any characters after the cursor move forward too. If the text in the buffer is `FOOBAR', with the cursor before the `B', then if you type XX, you get `FOOXXBAR', with the cursor still before the `B'.
To delete text you have just inserted, use DEL. DEL deletes the character before the cursor (not the one that the cursor is on top of or under; that is the character after the cursor). The cursor and all characters after it move backwards. Therefore, if you type a printing character and then type DEL, they cancel out.
To end a line and start typing a new one, type RET. This inserts a newline character in the buffer. If point is in the middle of a line, RET splits the line. Typing DEL when the cursor is at the beginning of a line rubs out the newline before the line, thus joining the line with the preceding line.
Emacs will split lines automatically when they become too long, if you turn on a special mode called Auto Fill mode. See section Filling Text, for how to use Auto Fill mode.
Customization information: DEL in most modes runs the command named
delete-backward-char; RET runs the command newline, and
self-inserting printing characters run the command self-insert,
which inserts whatever character was typed to invoke it. Some major modes
rebind DEL to other commands.
Direct insertion works for printing characters and SPC, but other
characters act as editing commands and do not insert themselves. If you
need to insert a control character or a character whose code is above 200
octal, you must quote it by typing the character control-q
(quoted-insert) first. There are two ways to use C-q:
A numeric argument to C-q specifies how many copies of the quoted character should be inserted (see section Numeric Arguments).
If you prefer to have text characters replace (overwrite) existing text rather than shove it to the right, you can enable Overwrite mode, a minor mode. See section Minor Modes.
To do more than insert characters, you have to know how to move point (see section Point). Here are a few of the commands for doing that.
beginning-of-line).
end-of-line).
forward-char).
backward-char).
forward-word).
backward-word).
next-line). This command
attempts to keep the horizontal position unchanged, so if you start in
the middle of one line, you end in the middle of the next. When on
the last line of text, C-n creates a new line and moves onto it.
previous-line).
recenter). Text moves
on the screen to bring point to the center of the window.
move-to-window-line). Text does not move on the
screen. A numeric argument says how many screen lines down from the
top of the window (zero for the top). A negative argument counts from
the bottom (-1 for the bottom).
transpose-chars).
beginning-of-buffer). With
numeric argument n, move to n/10 of the way from the top.
See section Numeric Arguments, for more information on numeric arguments.end-of-buffer).
set-goal-column). Henceforth, those
commands always move to this column in each line moved into, or as
close as possible given the contents of the line. This goal column remains
in effect until canceled.
If you set the variable track-eol to a non-nil value, then
C-n and C-p when at the end of the starting line move to the
end of the line. Normally, track-eol is nil.
delete-backward-char).
delete-char).
kill-line).
kill-word).
backward-kill-word).
You already know about the DEL key which deletes the character before the cursor. Another key, Control-d, deletes the character after the cursor, causing the rest of the text on the line to shift left. If Control-d is typed at the end of a line, that line and the next line are joined together.
To erase a larger amount of text, use the Control-k key, which kills a line at a time. If C-k is done at the beginning or middle of a line, it kills all the text up to the end of the line. If C-k is done at the end of a line, it joins that line and the next line.
See section Deletion and Killing, for more flexible ways of killing text.
The commands above are sufficient for creating and altering text in an Emacs buffer; the more advanced Emacs commands just make things easier. But to keep any text permanently you must put it in a file. Files are named units of text which are stored by the operating system for you to retrieve later by name. To look at or use the contents of a file in any way, including editing the file with Emacs, you must specify the file name.
Consider a file named `/usr/rms/foo.c'. In Emacs, to begin editing this file, type
C-x C-f /usr/rms/foo.c RET
Here the file name is given as an argument to the command C-x
C-f (find-file). That command uses the minibuffer to
read the argument, and you type RET to terminate the argument
(see section The Minibuffer).
Emacs obeys the command by visiting the file: creating a buffer,
copying the contents of the file into the buffer, and then displaying the
buffer for you to edit. You can make changes in it, and then save
the file by typing C-x C-s (save-buffer). This makes the
changes permanent by copying the altered contents of the buffer back into
the file `/usr/rms/foo.c'. Until then, the changes are only inside
your Emacs, and the file `foo.c' is not changed.
To create a file, just visit the file with C-x C-f as if it already existed. Emacs will make an empty buffer in which you can insert the text you want to put in the file. When you save your text with C-x C-s, the file will be created.
Of course, there is a lot more to learn about using files. See section File Handling.
If you forget what a key does, you can find out with the Help character,
which is C-h. Type C-h k followed by the key you want to know
about; for example, C-h k C-n tells you all about what C-n
does. C-h is a prefix key; C-h k is just one of its
subcommands (the command describe-key). The other subcommands of
C-h provide different kinds of help. Type C-h three times
to get a description of all the help facilities. See section Help.
Here are special commands and techniques for putting in and taking out blank lines.
open-line).
delete-blank-lines).
When you want to insert a new line of text before an existing line, you
can do it by typing the new line of text, followed by RET. However,
it may be easier to see what you are doing if you first make a blank line
and then insert the desired text into it. This is easy to do using the key
C-o (open-line), which inserts a newline after point but leaves
point in front of the newline. After C-o, type the text for the new
line. C-o F O O has the same effect as F O O RET, except for
the final location of point.
You can make several blank lines by typing C-o several times, or by giving it an argument to tell it how many blank lines to make. See section Numeric Arguments, for how.
If you have many blank lines in a row and want to get rid of them, use
C-x C-o (delete-blank-lines). When point is on a blank line which
is adjacent to at least one other blank line, C-x C-o deletes all but
one of the consecutive blank lines, leaving exactly one. With point on a
blank line with no other blank line adjacent to it, the sole blank line is
deleted, leaving none. When point is on a nonblank line, C-x C-o
deletes any blank lines following that nonblank line.
If you add too many characters to one line, without breaking it with a RET, the line will grow to occupy two (or more) lines on the screen, with a `\' at the extreme right margin of all but the last of them. The `\' says that the following screen line is not really a distinct line in the text, but just the continuation of a line too long to fit the screen. Sometimes it is nice to have Emacs insert newlines automatically when a line gets too long; for this, use Auto Fill mode (see section Filling Text).
Instead of continuation, long lines can be displayed by truncation. This means that all the characters that do not fit in the width of the screen or window do not appear at all. They remain in the buffer, temporarily invisible. `$' is used in the last column instead of `\' to inform you that truncation is in effect.
Continuation can be turned off for a particular buffer by setting the
variable truncate-lines to non-nil in that buffer.
Truncation instead of continuation also happens whenever horizontal
scrolling is in use, and optionally whenever side-by-side windows are in
use (see section Multiple Windows). Altering the value of truncate-lines makes
it local to the current buffer; until that time, the default value is in
effect. The default is initially nil. See section Local Variables.
If you are accustomed to other display editors, you may be surprised that Emacs does not always display the page number or line number of point in the mode line. This is because the text is stored in a way that makes it difficult to compute this information. Displaying them all the time would be intolerably slow. They are not needed very often in Emacs anyway, but there are commands to compute them and print them.
count-lines-region).
what-cursor-position).
There are two commands for printing line numbers. M-x what-line counts lines from the beginning of the file and prints the line number point is on. The first line of the file is line number 1. These numbers can be used as arguments to M-x goto-line. By contrast, M-x what-page counts pages from the beginning of the file, and counts lines within the page, printing both of them. See section Pages.
While on this subject, we might as well mention M-= (count-lines-region),
which prints the number of lines in the region (see section The Mark and the Region).
See section Pages, for the command C-x l which counts the lines in the
current page.
The command C-x = (what-cursor-position) can be used to find out
the column that the cursor is in, and other miscellaneous information about
point. It prints a line in the echo area that looks like this:
Char: x (0170) point=65986 of 563027(12%) x=44
(In fact, this is the output produced when point is before the `x=44' in the example.)
The two values after `Char:' describe the character following point, first by showing it and second by giving its octal character code.
`point=' is followed by the position of point expressed as a character count. The front of the buffer counts as position 1, one character later as 2, and so on. The next, larger number is the total number of characters in the buffer. Afterward in parentheses comes the position expressed as a percentage of the total size.
`x=' is followed by the horizontal position of point, in columns from the left edge of the window.
If the buffer has been narrowed, making some of the text at the beginning and the end temporarily invisible, C-x = prints additional text describing the current visible range. For example, it might say
Char: x (0170) point=65986 of 563025(12%) <65102 - 68533> x=44
where the two extra numbers give the smallest and largest character position that point is allowed to assume. The characters between those two positions are the visible ones. See section Narrowing.
If point is at the end of the buffer (or the end of the visible part), C-x = omits any description of the character after point. The output looks like
point=563026 of 563025(100%) x=0
Any Emacs command can be given a numeric argument. Some commands
interpret the argument as a repetition count. For example, giving an
argument of ten to the key C-f (the command forward-char, move
forward one character) moves forward ten characters. With these commands,
no argument is equivalent to an argument of one. Negative arguments are
allowed. Often they tell a command to move or act backwards.
If your terminal keyboard has a META key, the easiest way to specify a numeric argument is to type digits and/or a minus sign while holding down the the META key. For example,
M-5 C-n
would move down five lines. The characters Meta-1, Meta-2, and
so on, as well as Meta--, do this because they are keys bound to
commands (digit-argument and negative-argument) that are
defined to contribute to an argument for the next command.
Another way of specifying an argument is to use the C-u
(universal-argument) command followed by the digits of the argument.
With C-u, you can type the argument digits without holding
down shift keys. To type a negative argument, start with a minus sign.
Just a minus sign normally means -1. C-u works on all terminals.
C-u followed by a character which is neither a digit nor a minus sign has the special meaning of "multiply by four". It multiplies the argument for the next command by four. C-u twice multiplies it by sixteen. Thus, C-u C-u C-f moves forward sixteen characters. This is a good way to move forward "fast", since it moves about 1/5 of a line in the usual size screen. Other useful combinations are C-u C-n, C-u C-u C-n (move down a good fraction of a screen), C-u C-u C-o (make "a lot" of blank lines), and C-u C-k (kill four lines).
Some commands care only about whether there is an argument, and not about
its value. For example, the command M-q (fill-paragraph) with
no argument fills text; with an argument, it justifies the text as well.
(See section Filling Text, for more information on M-q.) Just C-u is a
handy way of providing an argument for such commands.
Some commands use the value of the argument as a repeat count, but do
something peculiar when there is no argument. For example, the command
C-k (kill-line) with argument n kills n lines,
including their terminating newlines. But C-k with no argument is
special: it kills the text up to the next newline, or, if point is right at
the end of the line, it kills the newline itself. Thus, two C-k
commands with no arguments can kill a nonblank line, just like C-k
with an argument of one. (See section Deletion and Killing, for more information on
C-k.)
A few commands treat a plain C-u differently from an ordinary argument. A few others may treat an argument of just a minus sign differently from an argument of -1. These unusual cases will be described when they come up; they are always for reasons of convenience of use of the individual command.
Emacs allows all changes made in the text of a buffer to be undone,
up to a certain amount of change (8000 characters). Each buffer records
changes individually, and the undo command always applies to the
current buffer. Usually each editing command makes a separate entry
in the undo records, but some commands such as query-replace
make many entries, and very simple commands such as self-inserting
characters are often grouped to make undoing less tedious.
undo).
The command C-x u or C-_ is how you undo. The first time you give this command, it undoes the last change. Point moves to the text affected by the undo, so you can see what was undone.
Consecutive repetitions of the C-_ or C-x u commands undo earlier and earlier changes, back to the limit of what has been recorded. If all recorded changes have already been undone, the undo command prints an error message and does nothing.
Any command other than an undo command breaks the sequence of undo commands. Starting at this moment, the previous undo commands are considered ordinary changes that can themselves be undone. Thus, you can redo changes you have undone by typing C-f or any other command that will have no important effect, and then using more undo commands.
If you notice that a buffer has been modified accidentally, the easiest way to recover is to type C-_ repeatedly until the stars disappear from the front of the mode line. At this time, all the modifications you made have been cancelled. If you do not remember whether you changed the buffer deliberately, type C-_ once, and when you see the last change you made undone, you will remember why you made it. If it was an accident, leave it undone. If it was deliberate, redo the change as described in the preceding paragraph.
Whenever an undo command makes the stars disappear from the mode line, it means that the buffer contents are the same as they were when the file was last read in or saved.
Not all buffers record undo information. Buffers whose names start with spaces don't; these buffers are used internally by Emacs and its extensions to hold text that users don't normally look at or edit. Also, minibuffers, help buffers and documentation buffers don't record undo information.
At most 8000 or so characters of deleted or modified text can be remembered in any one buffer for reinsertion by the undo command. Also, there is a limit on the number of individual insert, delete or change actions that can be remembered.
The reason the undo command has two keys, C-x u and C-_, set
up to run it is that it is worthy of a single-character key, but the way to
type C-_ on some keyboards is not obvious. C-x u is an alternative
you can type in the same fashion on any terminal.
The minibuffer is the facility used by Emacs commands to read arguments more complicated than a single number. Minibuffer arguments can be file names, buffer names, Lisp function names, Emacs command names, Lisp expressions, and many other things, depending on the command reading the argument. The usual Emacs editing commands can be used in the minibuffer to edit the argument.
When the minibuffer is in use, it appears in the echo area, and the terminal's cursor moves there. The beginning of the minibuffer line displays a prompt which says what kind of input you should supply and how it will be used. Often this prompt is derived from the name of the command that the argument is for. The prompt normally ends with a colon.
Sometimes a default argument appears in parentheses after the colon; it too is part of the prompt. The default will be used as the argument value if you enter an empty argument (e.g., just type RET). For example, commands that read buffer names always show a default, which is the name of the buffer that will be used if you type just RET.
The simplest way to give a minibuffer argument is to type the text you want, terminated by RET which exits the minibuffer. You can get out of the minibuffer, canceling the command that it was for, by typing C-g.
Since the minibuffer uses the screen space of the echo area, it can conflict with other ways Emacs customarily uses the echo area. Here is how Emacs handles such conflicts:
Sometimes the minibuffer starts out with text in it. For example, when you are supposed to give a file name, the minibuffer starts out containing the default directory, which ends with a slash. This is to inform you which directory the file will be found in if you do not specify a directory. For example, the minibuffer might start out with
Find File: /u2/emacs/src/
where `Find File: ' is the prompt. Typing buffer.c specifies the file `/u2/emacs/src/buffer.c'. To find files in nearby directories, use ..; thus, if you type ../lisp/simple.el, the file that you visit will be the one named `/u2/emacs/lisp/simple.el'. Alternatively, you can kill with M-DEL the directory names you don't want (see section Words).
You can also type an absolute file name, one starting with a slash or a tilde, ignoring the default directory. For example, to find the file `/etc/termcap', just type the name, giving
Find File: /u2/emacs/src//etc/termcap
Two slashes in a row are not normally meaningful in Unix file names, but they are allowed in GNU Emacs. They mean, "ignore everything before the second slash in the pair." Thus, `/u2/emacs/src/' is ignored, and you get the file `/etc/termcap'.
If you set insert-default-directory to nil, the default directory
is not inserted in the minibuffer. This way, the minibuffer starts out
empty. But the name you type, if relative, is still interpreted with
respect to the same default directory.
The minibuffer is an Emacs buffer (albeit a peculiar one), and the usual Emacs commands are available for editing the text of an argument you are entering.
Since RET in the minibuffer is defined to exit the minibuffer, inserting a newline into the minibuffer must be done with C-o or with C-q LFD. (Recall that a newline is really the LFD character.)
The minibuffer has its own window which always has space on the screen but acts as if it were not there when the minibuffer is not in use. When the minibuffer is in use, its window is just like the others; you can switch to another window with C-x o, edit text in other windows and perhaps even visit more files, before returning to the minibuffer to submit the argument. You can kill text in another window, return to the minibuffer window, and then yank the text to use it in the argument. See section Multiple Windows.
There are some restrictions on the use of the minibuffer window, however. You cannot switch buffers in it--the minibuffer and its window are permanently attached. Also, you cannot split or kill the minibuffer window. But you can make it taller in the normal fashion with C-x ^.
If while in the minibuffer you issue a command that displays help text of any sort in another window, then that window is identified as the one to scroll if you type C-M-v while in the minibuffer. This lasts until you exit the minibuffer. This feature comes into play if a completing minibuffer gives you a list of possible completions.
Recursive use of the minibuffer is supported by Emacs. However, it is easy to do this by accident (because of autorepeating keyboards, for example) and get confused. Therefore, most Emacs commands that use the minibuffer refuse to operate if the minibuffer window is selected. If the minibuffer is active but you have switched to a different window, recursive use of the minibuffer is allowed--if you know enough to try to do this, you probably will not get confused.
If you set the variable enable-recursive-minibuffers to be
non-nil, recursive use of the minibuffer is always allowed.
When appropriate, the minibuffer provides a completion facility. This means that you type enough of the argument to determine the rest, based on Emacs's knowledge of which arguments make sense, and Emacs visibly fills in the rest, or as much as can be determined from the part you have typed.
When completion is available, certain keys---TAB, RET, and SPC---are redefined to complete an abbreviation present in the minibuffer into a longer string that it stands for, by matching it against a set of completion alternatives provided by the command reading the argument. ? is defined to display a list of possible completions of what you have inserted.
For example, when the minibuffer is being used by Meta-x to read the name of a command, it is given a list of all available Emacs command names to complete against. The completion keys match the text in the minibuffer against all the command names, find any additional characters of the name that are implied by the ones already present in the minibuffer, and add those characters to the ones you have given.
Case is normally significant in completion, because it is significant in most of the names that you can complete (buffer names, file names and command names). Thus, `fo' will not complete to `Foo'. When you are completing a name in which case does not matter, case may be ignored for completion's sake if the program said to do so.
A concrete example may help here. If you type Meta-x au TAB,
the TAB looks for alternatives (in this case, command names) that
start with `au'. There are only two: auto-fill-mode and
auto-save-mode. These are the same as far as auto-, so the
`au' in the minibuffer changes to `auto-'.
If you type TAB again immediately, there are multiple possibilities for the very next character--it could be `s' or `f'---so no more characters are added; but a list of all possible completions is displayed in another window.
If you go on to type f TAB, this TAB sees
`auto-f'. The only command name starting this way is
auto-fill-mode, so completion inserts the rest of that. You
now have `auto-fill-mode' in the minibuffer after typing just au
TAB f TAB. Note that TAB has this effect because in the
minibuffer it is bound to the function minibuffer-complete when
completion is supposed to be done.
Here is a list of all the completion commands, defined in the minibuffer when completion is available.
minibuffer-complete).
minibuffer-complete-word).
minibuffer-complete-and-exit).
minibuffer-list-completions).
SPC completes much like TAB, but never goes beyond the
next hyphen or space. If you have `auto-f' in the minibuffer and type
SPC, it finds that the completion is `auto-fill-mode', but it
stops completing after `fill-'. This gives `auto-fill-'.
Another SPC at this point completes all the way to
`auto-fill-mode'. SPC in the minibuffer runs the function
minibuffer-complete-word when completion is available.
There are three different ways that RET can work in completing minibuffers, depending on how the argument will be used.
The completion commands display a list of all possible completions in a window whenever there is more than one possibility for the very next character. Also, typing ? explicitly requests such a list. The list of completions counts as help text, so C-M-v typed in the minibuffer scrolls the list.
When completion is done on file names, certain file names are usually
ignored. The variable completion-ignored-extensions contains a list
of strings; a file whose name ends in any of those strings is ignored as a
possible completion. The standard value of this variable has several
elements including ".o", ".elc", ".dvi" and "~".
The effect is that, for example, `foo' can complete to `foo.c'
even though `foo.o' exists as well. If the only possible completions
are files that end in "ignored" strings, then they are not ignored.
Normally, a completion command that finds the next character is undetermined
automatically displays a list of all possible completions. If the variable
completion-auto-help is set to nil, this does not happen,
and you must type ? to display the possible completions.
Every command that uses the minibuffer at least once is recorded on a special history list, together with the values of the minibuffer arguments, so that you can repeat the command easily. In particular, every use of Meta-x is recorded, since M-x uses the minibuffer to read the command name.
repeat-complex-command).
previous-complex-command).
next-complex-command).
C-x ESC is used to re-execute a recent minibuffer-using command. With no argument, it repeats the last such command. A numeric argument specifies which command to repeat; one means the last one, and larger numbers specify earlier ones.
C-x ESC works by turning the previous command into a Lisp expression and then entering a minibuffer initialized with the text for that expression. If you type just RET, the command is repeated as before. You can also change the command by editing the Lisp expression. Whatever expression you finally submit is what will be executed. The repeated command is added to the front of the command history unless it is identical to the most recently executed command already there.
Even if you don't understand Lisp syntax, it will probably be obvious which command is displayed for repetition. If you do not change the text, you can be sure it will repeat exactly as before.
Once inside the minibuffer for C-x ESC, if the command shown to you is not the one you want to repeat, you can move around the list of previous commands using M-n and M-p. M-p replaces the contents of the minibuffer with the next earlier recorded command, and M-n replaces them with the next later command. After finding the desired previous command, you can edit its expression as usual and then resubmit it by typing RET as usual. Any editing you have done on the command to be repeated is lost if you use M-n or M-p.
M-p is more useful than M-n, since more often you will
initially request to repeat the most recent command and then decide to
repeat an older one instead. These keys are specially defined within
C-x ESC to run the commands previous-complex-command and
next-complex-command.
The list of previous minibuffer-using commands is stored as a Lisp list
in the variable command-history. Each element is a Lisp expression
which describes one command and its arguments. Lisp programs can reexecute
a command by feeding the corresponding command-history element to
eval.
The Emacs commands that are used often or that must be quick to type are bound to keys--short sequences of characters--for convenient use. Other Emacs commands that do not need to be brief are not bound to keys; to run them, you must refer to them by name.
A command name is, by convention, made up of one or more words, separated
by hyphens; for example, auto-fill-mode or manual-entry. The
use of English words makes the command name easier to remember than a key
made up of obscure characters, even though it is more characters to type.
Any command can be run by name, even if it is also runnable by keys.
The way to run a command by name is to start with M-x, type the command name, and finish it with RET. M-x uses the minibuffer to read the command name. RET exits the minibuffer and runs the command.
Emacs uses the minibuffer for reading input for many different purposes; on this occasion, the string `M-x' is displayed at the beginning of the minibuffer as a prompt to remind you that your input should be the name of a command to be run. See section The Minibuffer, for full information on the features of the minibuffer.
You can use completion to enter the command name. For example, the
command forward-char can be invoked by name by typing
M-x forward-char RET or M-x fo TAB c RET
Note that forward-char is the same command that you invoke with
the key C-f. Any command (interactively callable function) defined
in Emacs can be called by its name using M-x whether or not any
keys are bound to it.
If you type C-g while the command name is being read, you cancel the M-x command and get out of the minibuffer, ending up at top level.
To pass a numeric argument to the command you are invoking with M-x, specify the numeric argument before the M-x. M-x passes the argument along to the function which it calls. The argument value appears in the prompt while the command name is being read.
Normally, when describing a command that is run by name, we omit the RET that is needed to terminate the name. Thus we might speak of M-x auto-fill-mode rather than M-x auto-fill-mode RET. We mention the RET only when there is a need to emphasize its presence, such as when describing a sequence of input that contains a command name and arguments that follow it.
M-x is defined to run the command execute-extended-command,
which is responsible for reading the name of another command and invoking
it.
Emacs provides extensive help features which revolve around a single character, C-h. C-h is a prefix key that is used only for documentation-printing commands. The characters that you can type after C-h are called help options. One help option is C-h; that is how you ask for help about using C-h.
C-h C-h prints a list of the possible help options, and then asks you to go ahead and type the option. It prompts with a string
A, B, C, F, I, K, L, M, N, S, T, V, W, C-c, C-d, C-n, C-w or C-h for more help:
and you should type one of those characters.
Typing a third C-h displays a description of what the options mean; it still waits for you to type an option. To cancel, type C-g.
Here is a summary of the defined help commands.
command-apropos).
describe-bindings).
describe-key-briefly).
c is for `character'. For more extensive information on key,
use C-h k.
describe-function). Note that commands are Lisp functions, so
a command name may be used.
info).
The complete Emacs manual is available on-line in Info.
describe-key).
view-lossage).
describe-mode).
view-emacs-news).
describe-syntax).
help-with-tutorial).
describe-variable).
where-is).
The most basic C-h options are C-h c
(describe-key-briefly) and C-h k (describe-key).
C-h c key prints in the echo area the name of the command that
key is bound to. For example, C-h c C-f prints
`forward-char'. Since command names are chosen to describe what the
command does, this is a good way to get a very brief description of what
key does.
C-h k key is similar but gives more information. It displays the documentation string of the command key is bound to as well as its name. This is too big for the echo area, so a window is used for the display.
C-h f (describe-function) reads the name of a Lisp function
using the minibuffer, then displays that function's documentation string
in a window. Since commands are Lisp functions, you can use this to get
the documentation of a command that is known by name. For example,
C-h f auto-fill-mode RET
displays the documentation of auto-fill-mode. This is the only
way to see the documentation of a command that is not bound to any key
(one which you would normally call using M-x).
C-h f is also useful for Lisp functions that you are planning to
use in a Lisp program. For example, if you have just written the code
(make-vector len) and want to be sure that you are using
make-vector properly, type C-h f make-vector RET. Because
C-h f allows all function names, not just command names, you may find
that some of your favorite abbreviations that work in M-x don't work
in C-h f. An abbreviation may be unique among command names yet fail
to be unique when other function names are allowed.
The function name for C-h f to describe has a default which is
used if you type RET leaving the minibuffer empty. The default is
the function called by the innermost Lisp expression in the buffer around
point, provided that is a valid, defined Lisp function name. For
example, if point is located following the text `(make-vector (car
x)', the innermost list containing point is the one that starts with
`(make-vector', so the default is to describe the function
make-vector.
C-h f is often useful just to verify that you have the right spelling for the function name. If C-h f mentions a default in the prompt, you have typed the name of a defined Lisp function. If that tells you what you want to know, just type C-g to cancel the C-h f command and go on editing.
C-h w command RET tells you what keys are bound to command. It prints a list of the keys in the echo area. Alternatively, it says that the command is not on any keys, which implies that you must use M-x to call it.
C-h v (describe-variable) is like C-h f but describes
Lisp variables instead of Lisp functions. Its default is the Lisp symbol
around or before point, but only if that is the name of a known Lisp
variable. See section Variables.
A more sophisticated sort of question to ask is, "What are the commands
for working with files?" For this, type C-h a file RET, which
displays a list of all command names that contain `file', such as
copy-file, find-file, and so on. With each command name
appears a brief description of how to use the command, and what keys you
can currently invoke it with. For example, it would say that you can
invoke find-file by typing C-x C-f. The a in C-h
a stands for `Apropos'; C-h a runs the Lisp function
command-apropos.
Because C-h a looks only for functions whose names contain the string which you specify, you must use ingenuity in choosing the string. If you are looking for commands for killing backwards and C-h a kill-backwards RET doesn't reveal any, don't give up. Try just kill, or just backwards, or just back. Be persistent. Pretend you are playing Adventure. Also note that you can use a regular expression as the argument (see section Syntax of Regular Expressions).
Here is a set of arguments to give to C-h a that covers many
classes of Emacs commands, since there are strong conventions for naming
the standard Emacs commands. By giving you a feel for the naming
conventions, this set should also serve to aid you in developing a
technique for picking apropos strings.
char, line, word, sentence, paragraph, region, page, sexp, list, defun, buffer, screen, window, file, dir, register, mode, beginning, end, forward, backward, next, previous, up, down, search, goto, kill, delete, mark, insert, yank, fill, indent, case, change, set, what, list, find, view, describe.
To list all Lisp symbols that contain a match for a regexp, not just the ones that are defined as commands, use the command M-x apropos instead of C-h a.
C-h i (info) runs the Info program, which is used for
browsing through structured documentation files. The entire Emacs manual
is available within Info. Eventually all the documentation of the GNU
system will be available. Type h after entering Info to run
a tutorial on using Info.
If something surprising happens, and you are not sure what commands you
typed, use C-h l (view-lossage). C-h l prints the last
100 command characters you typed in. If you see commands that you don't
know, you can use C-h c to find out what they do.
Emacs has several major modes, each of which redefines a few keys and
makes a few other changes in how editing works. C-h m (describe-mode)
prints documentation on the current major mode, which normally describes
all the commands that are changed in this mode.
C-h b (describe-bindings) and C-h s
(describe-syntax) present other information about the current
Emacs mode. C-h b displays a list of all the key bindings now
in effect; the local bindings of the current major mode first,
followed by the global bindings (see section Customizing Key Bindings). C-h s
displays the contents of the syntax table, with explanations of each
character's syntax (see section The Syntax Table).
The other C-h options display various files of useful
information. C-h C-w displays the full details on the complete
absence of warranty for GNU Emacs. C-h n (view-emacs-news)
displays the file `emacs/etc/NEWS', which contains documentation on
Emacs changes arranged chronologically. C-h t
(help-with-tutorial) displays the learn-by-doing Emacs tutorial.
C-h C-c (describe-copying) displays the file
`emacs/etc/COPYING', which tells you the conditions you must obey
in distributing copies of Emacs. C-h C-d
(describe-distribution) displays another file named
`emacs/etc/DISTRIB', which tells you how you can order a copy of
the latest version of Emacs.
There are many Emacs commands which operate on an arbitrary contiguous part of the current buffer. To specify the text for such a command to operate on, you set the mark at one end of it, and move point to the other end. The text between point and the mark is called the region. You can move point or the mark to adjust the boundaries of the region. It doesn't matter which one is set first chronologically, or which one comes earlier in the text.
Once the mark has been set, it remains until it is set again at another place. The mark remains fixed with respect to the preceding character if text is inserted or deleted in the buffer. Each Emacs buffer has its own mark, so that when you return to a buffer that had been selected previously, it has the same mark it had before.
Many commands that insert text, such as C-y (yank) and
M-x insert-buffer, position the mark at one end of the inserted
text--the opposite end from where point is positioned, so that the region
contains the text just inserted.
Aside from delimiting the region, the mark is also useful for remembering
a spot that you may want to go back to. To make this feature more useful,
Emacs remembers 16 previous locations of the mark, in the mark ring.
Here are some commands for setting the mark:
set-mark-command).
exchange-point-and-mark).
For example, if you wish to convert part of the buffer to all upper-case,
you can use the C-x C-u (upcase-region) command, which operates
on the text in the region. You can first go to the beginning of the text
to be capitalized, type C-SPC to put the mark there, move to
the end, and then type C-x C-u. Or, you can set the mark at the end
of the text, move to the beginning, and then type C-x C-u. Most
commands that operate on the text in the region have the word region
in their names.
The most common way to set the mark is with the C-SPC command
(set-mark-command). This sets the mark where point is. Then you
can move point away, leaving the mark behind. It is actually incorrect to
speak of the character C-SPC; there is no such character. When
you type SPC while holding down CTRL, what you get on most
terminals is the character C-@. This is the key actually bound to
set-mark-command. But unless you are unlucky enough to have a
terminal where typing C-SPC does not produce C-@, you
might as well think of this character as C-SPC.
Since terminals have only one cursor, there is no way for Emacs to show
you where the mark is located. You have to remember. The usual solution
to this problem is to set the mark and then use it soon, before you forget
where it is. But you can see where the mark is with the command C-x
C-x (exchange-point-and-mark) which puts the mark where point was and
point where the mark was. The extent of the region is unchanged, but the
cursor and point are now at the previous location of the mark.
C-x C-x is also useful when you are satisfied with the location of point but want to move the mark; do C-x C-x to put point there and then you can move it. A second use of C-x C-x, if necessary, puts the mark at the new location with point back at its original location.
Once you have created an active region, you can do many things to the text in it:
There are commands for placing point and the mark around a textual object such as a word, list, paragraph or page.
mark-word). This command and
the following one do not move point.
mark-sexp).
mark-paragraph).
mark-defun).
mark-whole-buffer).
mark-page).
M-@ (mark-word) puts the mark at the end of the next word,
while C-M-@ (mark-sexp) puts it at the end of the next Lisp
expression. These characters allow you to save a little typing or
redisplay, sometimes.
Other commands set both point and mark, to delimit an object in the
buffer. M-h (mark-paragraph) moves point to the beginning of
the paragraph that surrounds or follows point, and puts the mark at the end
of that paragraph (see section Paragraphs). M-h does all that's
necessary if you wish to indent, case-convert, or kill a whole paragraph.
C-M-h (mark-defun) similarly puts point before and the mark
after the current or following defun (see section Defuns). C-x C-p
(mark-page) puts point before the current page (or the next or
previous, according to the argument), and mark at the end (see section Pages).
The mark goes after the terminating page delimiter (to include it), while
point goes after the preceding page delimiter (to exclude it). Finally,
C-x h (mark-whole-buffer) sets up the entire buffer as the
region, by putting point at the beginning and the mark at the end.
Aside from delimiting the region, the mark is also useful for remembering
a spot that you may want to go back to. To make this feature more useful,
Emacs remembers 16 previous locations of the mark, in the mark ring.
Most commands that set the mark push the old mark onto this ring. To
return to a marked location, use C-u C-SPC (or C-u C-@); this is
the command set-mark-command given a numeric argument. It moves
point to where the mark was, and restores the mark from the ring of former
marks. So repeated use of this command moves point to all of the old marks
on the ring, one by one. The marks you see go to the end of the ring,
so no marks are lost.
Each buffer has its own mark ring. All editing commands use the current buffer's mark ring. In particular, C-u C-SPC always stays in the same buffer.
Many commands that can move long distances, such as M-<
(beginning-of-buffer), start by setting the mark and saving the old
mark on the mark ring. This is to make it easier for you to move back
later. Searches do this except when they do not actually move point. You
can tell when a command sets the mark because `Mark Set' is printed in
the echo area.
The variable mark-ring-max is the maximum number of entries to
keep in the mark ring. If that many entries exist and another one is
pushed, the last one in the list is discarded. Repeating C-u
C-SPC circulates through the limited number of entries that are
currently in the ring.
The variable mark-ring holds the mark ring itself, as a list of
marker objects in the order most recent first. This variable is local
in every buffer.
Killing means erasing text and copying it into the kill ring, from which it can be retrieved by yanking it. Some other systems that have recently become popular use the terms "cutting" and "pasting" for these operations.
The commonest way of moving or copying text with Emacs is to kill it and later yank it in one or more places. This is very safe because all the text killed recently is remembered, and it is versatile, because the many commands for killing syntactic units can also be used for moving those units. There are also other ways of copying text for special purposes.
Emacs has only one kill ring, so you can kill text in one buffer and yank it in another buffer.
Most commands which erase text from the buffer save it so that you can get it back if you change your mind, or move or copy it to other parts of the buffer. These commands are known as kill commands. The rest of the commands that erase text do not save it; they are known as delete commands. (This distinction is made only for erasure of text in the buffer.)
The delete commands include C-d (delete-char) and
DEL (delete-backward-char), which delete only one character at
a time, and those commands that delete only spaces or newlines. Commands
that can destroy significant amounts of nontrivial data generally kill.
The commands' names and individual descriptions use the words `kill'
and `delete' to say which they do. If you do a kill or delete command
by mistake, you can use the C-x u (undo) command to undo it
(see section Undoing Changes).
delete-char).
delete-backward-char).
delete-horizontal-space).
just-one-space).
delete-blank-lines).
delete-indentation).
The most basic delete commands are C-d (delete-char) and
DEL (delete-backward-char). C-d deletes the character
after point, the one the cursor is "on top of". Point doesn't move.
DEL deletes the character before the cursor, and moves point back.
Newlines can be deleted like any other characters in the buffer; deleting a
newline joins two lines. Actually, C-d and DEL aren't always
delete commands; if given an argument, they kill instead, since they can
erase more than one character this way.
The other delete commands are those which delete only formatting
characters: spaces, tabs and newlines. M-\ (delete-horizontal-space)
deletes all the spaces and tab characters before and after point.
M-SPC (just-one-space) does likewise but leaves a single
space after point, regardless of the number of spaces that existed
previously (even zero).
C-x C-o (delete-blank-lines) deletes all blank lines after
the current line, and if the current line is blank deletes all blank lines
preceding the current line as well (leaving one blank line, the current
line). M-^ (delete-indentation) joins the current line and
the previous line, or the current line and the next line if given an
argument, by deleting a newline and all surrounding spaces, possibly
leaving a single space. See section Indentation.
kill-line).
The simplest kill command is C-k. If given at the beginning of a line, it kills all the text on the line, leaving it blank. If given on a blank line, the blank line disappears. As a consequence, if you go to the front of a non-blank line and type C-k twice, the line disappears completely.
More generally, C-k kills from point up to the end of the line, unless it is at the end of a line. In that case it kills the newline following the line, thus merging the next line into the current one. Invisible spaces and tabs at the end of the line are ignored when deciding which case applies, so if point appears to be at the end of the line, you can be sure the newline will be killed.
If C-k is given a positive argument, it kills that many lines and the newlines that follow them (however, text on the current line before point is spared). With a negative argument, it kills back to a number of line beginnings. An argument of -2 means kill back to the second line beginning. If point is at the beginning of a line, that line beginning doesn't count, so C-u - 2 C-k with point at the front of a line kills the two previous lines.
C-k with an argument of zero kills all the text before point on the current line.
kill-region).
See section Words.
kill-word).
backward-kill-word).
backward-kill-sentence).
See section Sentences.
kill-sentence).
kill-sexp). See section Lists and Sexps.
zap-to-char).
A kill command which is very general is C-w (kill-region),
which kills everything between point and the mark. With this command, you
can kill any contiguous sequence of characters, if you first set the mark
at one end of them and go to the other end.
A convenient way of killing is combined with searching: M-z
(zap-to-char) reads a character and kills from point up to (but not
including) the next occurrence of that character in the buffer. If there
is no next occurrence, killing goes to the end of the buffer. A numeric
argument acts as a repeat count. A negative argument means to search
backward and kill text before point.
Other syntactic units can be killed: words, with M-DEL and M-d (see section Words); sexps, with C-M-k (see section Lists and Sexps); and sentences, with C-x DEL and M-k (see section Sentences).
Yanking is getting back text which was killed. This is what some systems call "pasting". The usual way to move or copy text is to kill it and then yank it one or more times.
yank).
yank-pop).
copy-region-as-kill).
append-next-kill).
All killed text is recorded in the kill ring, a list of blocks of text that have been killed. There is only one kill ring, used in all buffers, so you can kill text in one buffer and yank it in another buffer. This is the usual way to move text from one file to another. (See section Accumulating Text, for some other ways.)
The command C-y (yank) reinserts the text of the most recent
kill. It leaves the cursor at the end of the text. It sets the mark at
the beginning of the text. See section The Mark and the Region.
C-u C-y leaves the cursor in front of the text, and sets the mark after it. This is only if the argument is specified with just a C-u, precisely. Any other sort of argument, including C-u and digits, has an effect described below (under "Yanking Earlier Kills").
If you wish to copy a block of text, you might want to use M-w
(copy-region-as-kill), which copies the region into the kill ring
without removing it from the buffer. This is approximately equivalent to
C-w followed by C-y, except that M-w does not mark the
buffer as "modified" and does not temporarily change the screen.
Normally, each kill command pushes a new block onto the kill ring. However, two or more kill commands in a row combine their text into a single entry, so that a single C-y gets it all back as it was before it was killed. This means that you don't have to kill all the text in one command; you can keep killing line after line, or word after word, until you have killed it all, and you can still get it all back at once. (Thus we join television in leading people to kill thoughtlessly.)
Commands that kill forward from point add onto the end of the previous killed text. Commands that kill backward from point add onto the beginning. This way, any sequence of mixed forward and backward kill commands puts all the killed text into one entry without rearrangement. Numeric arguments do not break the sequence of appending kills. For example, suppose the buffer contains
This is the first line of sample text and here is the third.
with point at the beginning of the second line. If you type C-k C-u 2 M-DEL C-k, the first C-k kills the text `line of sample text', C-u 2 M-DEL kills `the first' with the newline that followed it, and the second C-k kills the newline after the second line. The result is that the buffer contains `This is and here is the third.' and a single kill entry contains `the firstRETline of sample textRET'---all the killed text, in its original order.
If a kill command is separated from the last kill command by other
commands (not just numeric arguments), it starts a new entry on the kill
ring. But you can force it to append by first typing the command
C-M-w (append-next-kill) in front of it. The C-M-w
tells the following command, if it is a kill command, to append the text it
kills to the last killed text, instead of starting a new entry. With
C-M-w, you can kill several separated pieces of text and accumulate
them to be yanked back in one place.
To recover killed text that is no longer the most recent kill, you need
the Meta-y (yank-pop) command. M-y can be used only
after a C-y or another M-y. It takes the text previously
yanked and replaces it with the text from an earlier kill. So, to recover
the text of the next-to-the-last kill, you first use C-y to recover
the last kill, and then use M-y to replace it with the previous
kill.
You can think in terms of a "last yank" pointer which points at an item in the kill ring. Each time you kill, the "last yank" pointer moves to the newly made item at the front of the ring. C-y yanks the item which the "last yank" pointer points to. M-y moves the "last yank" pointer to a different item, and the text in the buffer changes to match. Enough M-y commands can move the pointer to any item in the ring, so you can get any item into the buffer. Eventually the pointer reaches the end of the ring; the next M-y moves it to the first item again.
Yanking moves the "last yank" pointer around the ring, but it does not change the order of the entries in the ring, which always runs from the most recent kill at the front to the oldest one still remembered.
M-y can take a numeric argument, which tells it how many items to advance the "last yank" pointer by. A negative argument moves the pointer toward the front of the ring; from the front of the ring, it moves to the last entry and starts moving forward from there.
Once the text you are looking for is brought into the buffer, you can stop doing M-y commands and it will stay there. It's just a copy of the kill ring item, so editing it in the buffer does not change what's in the ring. As long as no new killing is done, the "last yank" pointer remains at the same place in the kill ring, so repeating C-y will yank another copy of the same old kill.
If you know how many M-y commands it would take to find the text you want, you can yank that text in one step using C-y with a numeric argument. C-y with an argument greater than one restores the text the specified number of entries back in the kill ring. Thus, C-u 2 C-y gets the next to the last block of killed text. It is equivalent to C-y M-y. C-y with a numeric argument starts counting from the "last yank" pointer, and sets the "last yank" pointer to the entry that it yanks.
The length of the kill ring is controlled by the variable
kill-ring-max; no more than that many blocks of killed text are
saved.
Usually we copy or move text by killing it and yanking it, but there are other ways that are useful for copying one block of text in many places, or for copying many scattered blocks of text into one place.
You can accumulate blocks of text from scattered locations either into a buffer or into a file if you like. These commands are described here. You can also use Emacs registers for storing and accumulating text. See section Registers.
append-to-buffer).
To accumulate text into a buffer, use the command C-x a buffername
(append-to-buffer), which inserts a copy of the region into the
buffer buffername, at the location of point in that buffer. If there
is no buffer with that name, one is created. If you append text into a
buffer which has been used for editing, the copied text goes into the
middle of the text of the buffer, wherever point happens to be in it.
Point in that buffer is left at the end of the copied text, so successive uses of C-x a accumulate the text in the specified buffer in the same order as they were copied. Strictly speaking, C-x a does not always append to the text already in the buffer; but if C-x a is the only command used to alter a buffer, it does always append to the existing text because point is always at the end.
M-x prepend-to-buffer is just like C-x a except that point in the other buffer is left before the copied text, so successive prependings add text in reverse order. M-x copy-to-buffer is similar except that any existing text in the other buffer is deleted, so the buffer is left containing just the text newly copied into it.
You can retrieve the accumulated text from that buffer with M-x insert-buffer; this too takes buffername as an argument. It inserts a copy of the text in buffer buffername into the selected buffer. You could alternatively select the other buffer for editing, perhaps moving text from it by killing or with C-x a. See section Using Multiple Buffers, for background information on buffers.
Instead of accumulating text within Emacs, in a buffer, you can append text directly into a file with M-x append-to-file, which takes file-name as an argument. It adds the text of the region to the end of the specified file. The file is changed immediately on disk. This command is normally used with files that are not being visited in Emacs. Using it on a file that Emacs is visiting can produce confusing results, because the text inside Emacs for that file will not change while the file itself changes.
The rectangle commands affect rectangular areas of the text: all the characters between a certain pair of columns, in a certain range of lines. Commands are provided to kill rectangles, yank killed rectangles, clear them out, or delete them. Rectangle commands are useful with text in multicolumnar formats, such as perhaps code with comments at the right, or for changing text into or out of such formats.
When you must specify a rectangle for a command to work on, you do it by putting the mark at one corner and point at the opposite corner. The rectangle thus specified is called the region-rectangle because it is controlled about the same way the region is controlled. But remember that a given combination of point and mark values can be interpreted either as specifying a region or as specifying a rectangle; it is up to the command that uses them to choose the interpretation.
The rectangle operations fall into two classes: commands deleting and moving rectangles, and commands for blank rectangles.
There are two ways to get rid of the text in a rectangle: you can discard the text (delete it) or save it as the "last killed" rectangle. The commands for these two ways are M-x delete-rectangle and M-x kill-rectangle. In either case, the portion of each line that falls inside the rectangle's boundaries is deleted, causing following text (if any) on the line to move left.
Note that "killing" a rectangle is not killing in the usual sense; the rectangle is not stored in the kill ring, but in a special place that can only record the most recent rectangle killed. This is because yanking a rectangle is so different from yanking linear text that different yank commands have to be used and yank-popping is hard to make sense of.
Inserting a rectangle is the opposite of deleting one. All you need to specify is where to put the upper left corner; that is done by putting point there. The rectangle's first line is inserted there, the rectangle's second line is inserted at a point one line vertically down, and so on. The number of lines affected is determined by the height of the saved rectangle.
To insert the last killed rectangle, type M-x yank-rectangle. This can be used to convert single-column lists into double-column lists; kill the second half of the list as a rectangle and then yank it beside the first line of the list.
There are two commands for working with blank rectangles: M-x clear-rectangle to blank out existing text, and M-x open-rectangle to insert a blank rectangle. Clearing a rectangle is equivalent to deleting it and then inserting as blank rectangle of the same size.
Rectangles can also be copied into and out of registers. See section Saving Rectangles in Registers.
Emacs registers are places you can save text or positions for later use. Text saved in a register can be copied into the buffer once or many times; a position saved in a register is used by moving point to that position. Rectangles can also be copied into and out of registers (see section Rectangles).
Each register has a name, which is a single character. A register can store either a piece of text or a position or a rectangle, but only one thing at any given time. Whatever you store in a register remains there until you store something else in that register.
M-x view-register reads a register name as an argument and then displays the contents of the specified register.
Saving a position records a spot in a buffer so that you can move back there later. Moving to a saved position reselects the buffer and moves point to the spot.
point-to-register).
register-to-point).
To save the current location of point in a register, choose a name r and type C-x / r. The register r retains the location thus saved until you store something else in that register.
The command C-x j r moves point to the location recorded in register r. The register is not affected; it continues to record the same location. You can jump to the same position using the same register any number of times.
When you want to insert a copy of the same piece of text frequently, it
may be impractical to use the kill ring, since each subsequent kill moves
the piece of text further down on the ring. It becomes hard to keep track
of what argument is needed to retrieve the same text with C-y. An
alternative is to store the text in a register with C-x x
(copy-to-register) and then retrieve it with C-x g
(insert-register).
copy-to-register).
insert-register).
C-x x r stores a copy of the text of the region into the register named r. Given a numeric argument, C-x x deletes the text from the buffer as well.
C-x g r inserts in the buffer the text from register r. Normally it leaves point before the text and places the mark after, but with a numeric argument it puts point after the text and the mark before.
A register can contain a rectangle instead of linear text. The rectangle is represented as a list of strings. See section Rectangles, for basic information on rectangles and how rectangles in the buffer are specified.
copy-region-to-rectangle).
With numeric argument, delete it as well.
insert-register).
The C-x g command inserts linear text if the register contains that, or inserts a rectangle if the register contains one.
Since only part of a large buffer fits in the window, Emacs tries to show the part that is likely to be interesting. The display control commands allow you to specify which part of the text you want to see.
recenter).
scroll-up).
scroll-down).
recenter).
scroll-left).
scroll-right).
set-selective-display).
If a buffer contains text that is too large to fit entirely within a window that is displaying the buffer, Emacs shows a contiguous section of the text. The section shown always contains point.
Scrolling means moving text up or down in the window so that different parts of the text are visible. Scrolling forward means that text moves up, and new text appears at the bottom. Scrolling backward moves text down and new text appears at the top.
Scrolling happens automatically if you move point past the bottom or top of the window. You can also explicitly request scrolling with the commands in this section.
The most basic scrolling command is C-l (recenter) with no
argument. It clears the entire screen and redisplays all windows. In
addition, the selected window is scrolled so that point is halfway down
from the top of the window.
The scrolling commands C-v and M-v let you move all the text
in the window up or down a few lines. C-v (scroll-up) with an
argument shows you that many more lines at the bottom of the window, moving
the text and point up together as C-l might. C-v with a
negative argument shows you more lines at the top of the window.
Meta-v (scroll-down) is like C-v, but moves in the
opposite direction.
To read the buffer a windowful at a time, use C-v with no argument.
It takes the last two lines at the bottom of the window and puts them at
the top, followed by nearly a whole windowful of lines not previously
visible. If point was in the text scrolled off the top, it moves to the
new top of the window. M-v with no argument moves backward with
overlap similarly. The number of lines of overlap across a C-v or
M-v is controlled by the variable next-screen-context-lines; by
default, it is two.
Another way to do scrolling is with C-l with a numeric argument. C-l does not clear the screen when given an argument; it only scrolls the selected window. With a positive argument n, it repositions text to put point n lines down from the top. An argument of zero puts point on the very top line. Point does not move with respect to the text; rather, the text and point move rigidly on the screen. C-l with a negative argument puts point that many lines from the bottom of the window. For example, C-u - 1 C-l puts point on the bottom line, and C-u - 5 C-l puts it five lines from the bottom. Just C-u as argument, as in C-u C-l, scrolls point to the center of the screen.
Scrolling happens automatically if point has moved out of the visible
portion of the text when it is time to display. Usually the scrolling is
done so as to put point vertically centered within the window. However, if
the variable scroll-step has a nonzero value, an attempt is made to
scroll the buffer by that many lines; if that is enough to bring point back
into visibility, that is what is done.
The text in a window can also be scrolled horizontally. This means that each line of text is shifted sideways in the window, and one or more characters at the beginning of each line are not displayed at all. When a window has been scrolled horizontally in this way, text lines are truncated rather than continued (see section Continuation Lines), with a `$' appearing in the first column when there is text truncated to the left, and in the last column when there is text truncated to the right.
The command C-x < (scroll-left) scrolls the selected window
to the left by n columns with argument n. With no argument, it scrolls
by almost the full width of the window (two columns less, to be precise).
C-x > (scroll-right) scrolls similarly to the right.
The window cannot be scrolled any farther to the right once it is
displaying normally (with each line starting at the window's left margin);
attempting to do so has no effect.
Emacs has the ability to hide lines indented more than a certain number of columns (you specify how many columns). You can use this to get an overview of a part of a program.
To hide lines, type C-x $ (set-selective-display) with a
numeric argument n. (See section Numeric Arguments, for how to give the
argument.) Then lines with at least n columns of indentation
disappear from the screen. The only indication of their presence is that
three dots (`...') appear at the end of each visible line that is
followed by one or more invisible ones.
The invisible lines are still present in the buffer, and most editing commands see them as usual, so it is very easy to put point in the middle of invisible text. When this happens, the cursor appears at the end of the previous line, after the three dots. If point is at the end of the visible line, before the newline that ends it, the cursor appears before the three dots.
The commands C-n and C-p move across the invisible lines as if they were not there.
To make everything visible again, type C-x $ with no argument.
This section contains information for customization only. Beginning users should skip it.
The variable mode-line-inverse-video controls whether the mode
line is displayed in inverse video (assuming the terminal supports it);
nil means don't do so. See section The Mode Line.
If the variable inverse-video is non-nil, Emacs attempts
to invert all the lines of the display from what they normally are.
If the variable visible-bell is non-nil, Emacs attempts
to make the whole screen blink when it would normally make an audible bell
sound. This variable has no effect if your terminal does not have a way
to make the screen blink.
When you reenter Emacs after suspending, Emacs normally clears the screen
and redraws the entire display. On some terminals with more than one page
of memory, it is possible to arrange the termcap entry so that the
`ti' and `te' strings (output to the terminal when Emacs is
entered and exited, respectively) switch between pages of memory so as to
use one page for Emacs and another page for other output. Then you might
want to set the variable no-redraw-on-reenter non-nil so that
Emacs will assume, when resumed, that the screen page it is using still
contains what Emacs last wrote there.
The variable echo-keystrokes controls the echoing of multi-character
keys; its value is the number of seconds of pause required to cause echoing
to start, or zero meaning don't echo at all. See section The Echo Area.
If the variable ctl-arrow is nil, control characters in the
buffer are displayed with octal escape sequences, all except newline and
tab. Altering the value of ctl-arrow makes it local to the current
buffer; until that time, the default value is in effect. The default is
initially t. See section Local Variables.
Normally, a tab character in the buffer is displayed as whitespace which
extends to the next display tab stop position, and display tab stops come
at intervals equal to eight spaces. The number of spaces per tab is
controlled by the variable tab-width, which is made local by
changing it, just like ctl-arrow. Note that how the tab character
in the buffer is displayed has nothing to do with the definition of
TAB as a command.
If you set the variable selective-display-ellipses to nil,
the three dots do not appear at the end of a line that precedes invisible
lines. Then there is no visible indication of the invisible lines.
This variable too becomes local automatically when set.
Like other editors, Emacs has commands for searching for occurrences of a string. The principal search command is unusual in that it is incremental; it begins to search before you have finished typing the search string. There are also nonincremental search commands more like those of other editors.
Besides the usual replace-string command that finds all
occurrences of one string and replaces them with another, Emacs has a fancy
replacement command called query-replace which asks interactively
which occurrences to replace.
An incremental search begins searching as soon as you type the first character of the search string. As you type in the search string, Emacs shows you where the string (as you have typed it so far) would be found. When you have typed enough characters to identify the place you want, you can stop. Depending on what you will do next, you may or may not need to terminate the search explicitly with an ESC first.
isearch-forward).
isearch-backward).
C-s starts an incremental search. C-s reads characters from the keyboard and positions the cursor at the first occurrence of the characters that you have typed. If you type C-s and then F, the cursor moves right after the first `F'. Type an O, and see the cursor move to after the first `FO'. After another O, the cursor is after the first `FOO' after the place where you started the search. Meanwhile, the search string `FOO' has been echoed in the echo area.
The echo area display ends with three dots when actual searching is going on. When search is waiting for more input, the three dots are removed. (On slow terminals, the three dots are not displayed.)
If you make a mistake in typing the search string, you can erase characters with DEL. Each DEL cancels the last character of search string. This does not happen until Emacs is ready to read another input character; first it must either find, or fail to find, the character you want to erase. If you do not want to wait for this to happen, use C-g as described below.
When you are satisfied with the place you have reached, you can type ESC, which stops searching, leaving the cursor where the search brought it. Also, any command not specially meaningful in searches stops the searching and is then executed. Thus, typing C-a would exit the search and then move to the beginning of the line. ESC is necessary only if the next command you want to type is a printing character, DEL, ESC, or another control character that is special within searches (C-q, C-w, C-r, C-s or C-y).
Sometimes you search for `FOO' and find it, but not the one you expected to find. There was a second `FOO' that you forgot about, before the one you were looking for. In this event, type another C-s to move to the next occurrence of the search string. This can be done any number of times. If you overshoot, you can cancel some C-s characters with DEL.
After you exit a search, you can search for the same string again by typing just C-s C-s: the first C-s is the key that invokes incremental search, and the second C-s means "search again".
If your string is not found at all, the echo area says `Failing I-Search'. The cursor is after the place where Emacs found as much of your string as it could. Thus, if you search for `FOOT', and there is no `FOOT', you might see the cursor after the `FOO' in `FOOL'. At this point there are several things you can do. If your string was mistyped, you can rub some of it out and correct it. If you like the place you have found, you can type ESC or some other Emacs command to "accept what the search offered". Or you can type C-g, which removes from the search string the characters that could not be found (the `T' in `FOOT'), leaving those that were found (the `FOO' in `FOOT'). A second C-g at that point cancels the search entirely, returning point to where it was when the search started.
If a search is failing and you ask to repeat it by typing another C-s, it starts again from the beginning of the buffer. Repeating a failing reverse search with C-r starts again from the end. This is called wrapping around. `Wrapped' appears in the search prompt once this has happened.
The C-g "quit" character does special things during searches; just what it does depends on the status of the search. If the search has found what you specified and is waiting for input, C-g cancels the entire search. The cursor moves back to where you started the search. If C-g is typed when there are characters in the search string that have not been found--because Emacs is still searching for them, or because it has failed to find them--then the search string characters which have not been found are discarded from the search string. With them gone, the search is now successful and waiting for more input, so a second C-g will cancel the entire search.
To search for a control character such as C-s or DEL or ESC, you must quote it by typing C-q first. This function of C-q is analogous to its meaning as an Emacs command: it causes the following character to be treated the way a graphic character would normally be treated in the same context.
You can change to searching backwards with C-r. If a search fails because the place you started was too late in the file, you should do this. Repeated C-r keeps looking for more occurrences backwards. A C-s starts going forwards again. C-r in a search can be cancelled with DEL.
If you know initially that you want to search backwards, you can
use C-r instead of C-s to start the search, because C-r
is also a key running a command (isearch-backward) to search
backward.
The characters C-y and C-w can be used in incremental search to grab text from the buffer into the search string. This makes it convenient to search for another occurrence of text at point. C-w copies the word after point as part of the search string, advancing point over that word. Another C-s to repeat the search will then search for a string including that word. C-y is similar to C-w but copies all the rest of the current line into the search string.
All the characters special in incremental search can be changed by setting the following variables:
search-delete-char
search-exit-char
search-quote-char
search-repeat-char
search-reverse-char
search-yank-line-char
search-yank-word-char
Incremental search on a slow terminal uses a modified style of display that is designed to take less time. Instead of redisplaying the buffer at each place the search gets to, it creates a new single-line window and uses that to display the line that the search has found. The single-line window comes into play as soon as point gets outside of the text that is already on the screen.
When the search is terminated, the single-line window is removed. Only at this time is the window in which the search was done redisplayed to show its new value of point.
The three dots at the end of the search string, normally used to indicate that searching is going on, are not displayed in slow style display.
The slow terminal style of display is used when the terminal baud rate is
less than or equal to the value of the variable search-slow-speed,
initially 1200.
The number of lines to use in slow terminal search display is controlled
by the variable search-slow-window-lines. 1 is its normal value.
Emacs also has conventional nonincremental search commands, which require you to type the entire search string before searching begins.
To do a nonincremental search, first type C-s ESC. This enters the minibuffer to read the search string; terminate the string with RET, and then the search is done. If the string is not found the search command gets an error.
The way C-s ESC works is that the C-s invokes incremental search, which is specially programmed to invoke nonincremental search if the argument you give it is empty. (Such an empty argument would otherwise be useless.) C-r ESC also works this way.
Forward and backward nonincremental searches are implemented by the
commands search-forward and search-backward. These commands
may be bound to keys in the usual manner. The reason that incremental
search is programmed to invoke them as well is that C-s ESC
is the traditional sequence of characters used in Emacs to invoke
nonincremental search.
However, nonincremental searches performed using C-s ESC do
not call search-forward right away. The first thing done is to see
if the next character is C-w, which requests a word search.
Word search searches for a sequence of words without regard to how the words are separated. More precisely, you type a string of many words, using single spaces to separate them, and the string can be found even if there are multiple spaces, newlines or other punctuation between the words.
Word search is useful in editing documents formatted by text formatters. If you edit while looking at the printed, formatted version, you can't tell where the line breaks are in the source file. With word search, you can search without having to know them.
Word search is a special case of nonincremental search and is invoked with C-s ESC C-w. This is followed by the search string, which must always be terminated with RET. Being nonincremental, this search does not start until the argument is terminated. It works by constructing a regular expression and searching for that. See section Regular Expression Search.
A backward word search can be done by C-r ESC C-w.
Forward and backward word searches are implemented by the commands
word-search-forward and word-search-backward. These commands
may be bound to keys in the usual manner. The reason that incremental
search is programmed to invoke them as well is that C-s ESC C-w
is the traditional Emacs sequence of keys for word search.
A regular expression (regexp, for short) is a pattern that denotes a set of strings, possibly an infinite set. Searching for matches for a regexp is a very powerful operation that editors on Unix systems have traditionally offered. In GNU Emacs, you can search for the next match for a regexp either incrementally or not.
Incremental search for a regexp is done by typing C-M-s
(isearch-forward-regexp). This command reads a search string
incrementally just like C-s, but it treats the search string as a
regexp rather than looking for an exact match against the text in the
buffer. Each time you add text to the search string, you make the regexp
longer, and the new regexp is searched for. A reverse regexp search command
isearch-backward-regexp also exists but no key runs it.
All of the control characters that do special things within an ordinary incremental search have the same function in incremental regexp search. Typing C-s or C-r immediately after starting the search retrieves the last incremental search regexp used; that is to say, incremental regexp and non-regexp searches have independent defaults.
Note that adding characters to the regexp in an incremental regexp search does not make the cursor move back and start again. Perhaps it ought to; I am not sure. As it stands, if you have searched for `foo' and you add `\|bar', the search will not check for a `bar' in the buffer before the `foo'.
Nonincremental search for a regexp is done by the functions
re-search-forward and re-search-backward. You can invoke
these with M-x, or bind them to keys. Also, you can call
re-search-forward by way of incremental regexp search with
C-M-s ESC.
Regular expressions have a syntax in which a few characters are special constructs and the rest are ordinary. An ordinary character is a simple regular expression which matches that character and nothing else. The special characters are `$', `^', `.', `*', `+', `?', `[', `]' and `\'; no new special characters will be defined. Any other character appearing in a regular expression is ordinary, unless a `\' precedes it.
For example, `f' is not a special character, so it is ordinary, and therefore `f' is a regular expression that matches the string `f' and no other string. (It does not match the string `ff'.) Likewise, `o' is a regular expression that matches only `o'.
Any two regular expressions a and b can be concatenated. The result is a regular expression which matches a string if a matches some amount of the beginning of that string and b matches the rest of the string.
As a simple example, we can concatenate the regular expressions `f' and `o' to get the regular expression `fo', which matches only the string `fo'. Still trivial. To do something nontrivial, you need to use one of the special characters. Here is a list of them.
Note: for historical compatibility, special characters are treated as ordinary ones if they are in contexts where their special meanings make no sense. For example, `*foo' treats `*' as ordinary since there is no preceding expression on which the `*' can act. It is poor practice to depend on this behavior; better to quote the special character anyway, regardless of where is appears.
For the most part, `\' followed by any character matches only that character. However, there are several exceptions: characters which, when preceded by `\', are special constructs. Such characters are always ordinary when encountered on their own. Here is a table of `\' constructs.
Here is a complicated regexp, used by Emacs to recognize the end of a sentence together with any whitespace that follows. It is given in Lisp syntax to enable you to distinguish the spaces from the tab characters. In Lisp syntax, the string constant begins and ends with a double-quote. `\"' stands for a double-quote as part of the regexp, `\\' for a backslash as part of the regexp, `\t' for a tab and `\n' for a newline.
"[.?!][]\"')]*\\($\\|\t\\| \\)[ \t\n]*"
This contains four parts in succession: a character set matching period, `?' or `!'; a character set matching close-brackets, quotes or parentheses, repeated any number of times; an alternative in backslash-parentheses that matches end-of-line, a tab or two spaces; and a character set matching whitespace characters, repeated any number of times.
All sorts of searches in Emacs normally ignore the case of the text they are searching through; if you specify searching for `FOO', then `Foo' and `foo' are also considered a match. Regexps, and in particular character sets, are included: `[aB]' would match `a' or `A' or `b' or `B'.
If you do not want this feature, set the variable case-fold-search
to nil. Then all letters must match exactly, including case. This
is a per-buffer variable; altering the variable affects only the current
buffer, but there is a default value which you can change as well.
See section Local Variables.
Global search-and-replace operations are not needed as often in Emacs as
they are in other editors, but they are available. In addition to the
simple replace-string command which is like that found in most
editors, there is a query-replace command which asks you, for each
occurrence of the pattern, whether to replace it.
The replace commands all replace one string (or regexp) with one
replacement string. It is possible to perform several replacements in
parallel using the command expand-region-abbrevs. See section Controlling Abbrev Expansion.
To replace every instance of `foo' after point with `bar', use the command M-x replace-string with the two arguments `foo' and `bar'. Replacement occurs only after point, so if you want to cover the whole buffer you must go to the beginning first. All occurrences up to the end of the buffer are replaced; to limit replacement to part of the buffer, narrow to that part of the buffer before doing the replacement (see section Narrowing).
When replace-string exits, point is left at the last occurrence
replaced. The value of point when the replace-string command was
issued is remembered on the mark ring; C-u C-SPC moves back
there.
A numeric argument restricts replacement to matches that are surrounded by word boundaries.
replace-string replaces exact matches for a single string. The
similar command replace-regexp replaces any match for a specified
pattern.
In replace-regexp, the newstring need not be constant. It
can refer to all or part of what is matched by the regexp. `\&'
in newstring stands for the entire text being replaced.
`\d' in newstring, where d is a digit, stands for
whatever matched the d'th parenthesized grouping in regexp.
For example,
M-x replace-regexp RET c[ad]+r RET \&-safe RET
would replace (for example) `cadr' with `cadr-safe' and `cddr' with `cddr-safe'.
M-x replace-regexp RET \(c[ad]+r\)-safe RET \1 RET
would perform exactly the opposite replacements. To include a `\' in the text to replace with, you must give `\\'.
If the arguments to a replace command are in lower case, it preserves case when it makes a replacement. Thus, the command
M-x replace-string RET foo RET bar RET
replaces a lower case `foo' with a lower case `bar', `FOO'
with `BAR', and `Foo' with `Bar'. If upper case letters are
used in the second argument, they remain upper case every time that
argument is inserted. If upper case letters are used in the first
argument, the second argument is always substituted exactly as given, with
no case conversion. Likewise, if the variable case-replace is set
to nil, replacement is done without case conversion. If
case-fold-search is set to nil, case is significant in
matching occurrences of `foo' to replace; also, case conversion of the
replacement string is not done.
If you want to change only some of the occurrences of `foo' to
`bar', not all of them, then you cannot use an ordinary
replace-string. Instead, use M-% (query-replace).
This command finds occurrences of `foo' one by one, displays each
occurrence and asks you whether to replace it. A numeric argument to
query-replace tells it to consider only occurrences that are bounded
by word-delimiter characters.
Aside from querying, query-replace works just like
replace-string, and query-replace-regexp works
just like replace-regexp.
The things you can type when you are shown an occurrence of string or a match for regexp are:
replace-string, provided case-replace is non-nil,
as it normally is.
query-replace, so if you want to do further replacement you must use
C-x ESC to restart (see section Repeating Minibuffer Commands).
query-replace.
If you type any other character, the query-replace is exited, and
the character executed as a command. To restart the query-replace,
use C-x ESC, which repeats the query-replace because it
used the minibuffer to read its arguments. See section Repeating Minibuffer Commands.
Here are some other commands that find matches for a regular expression. They all operate from point to the end of the buffer.
In this chapter we describe the commands that are especially useful for the times when you catch a mistake in your text just after you have made it, or change your mind while composing text on line.
delete-backward-char).
backward-kill-word).
backward-kill-sentence).
The DEL character (delete-backward-char) is the most
important correction command. When used among graphic (self-inserting)
characters, it can be thought of as canceling the last character typed.
When your mistake is longer than a couple of characters, it might be more convenient to use M-DEL or C-x DEL. M-DEL kills back to the start of the last word, and C-x DEL kills back to the start of the last sentence. C-x DEL is particularly useful when you are thinking of what to write as you type it, in case you change your mind about phrasing. M-DEL and C-x DEL save the killed text for C-y and M-y to retrieve. See section Yanking.
M-DEL is often useful even when you have typed only a few characters wrong, if you know you are confused in your typing and aren't sure exactly what you typed. At such a time, you cannot correct with DEL except by looking at the screen to see what you did. It requires less thought to kill the whole word and start over again.
transpose-chars).
transpose-words).
transpose-sexps).
transpose-lines).
The common error of transposing two characters can be fixed, when they
are adjacent, with the C-t command (transpose-chars). Normally,
C-t transposes the two characters on either side of point. When
given at the end of a line, rather than transposing the last character of
the line with the newline, which would be useless, C-t transposes the
last two characters on the line. So, if you catch your transposition error
right away, you can fix it with just a C-t. If you don't catch it so
fast, you must move the cursor back to between the two transposed
characters. If you transposed a space with the last character of the word
before it, the word motion commands are a good way of getting there.
Otherwise, a reverse search (C-r) is often the best way.
See section Searching and Replacement.
Meta-t (transpose-words) transposes the word before point
with the word after point. It moves point forward over a word, dragging
the word preceding or containing point forward as well. The punctuation
characters between the words do not move. For example, `FOO, BAR'
transposes into `BAR, FOO' rather than `BAR FOO,'.
C-M-t (transpose-sexps) is a similar command for transposing
two expressions (see section Lists and Sexps), and C-x C-t (transpose-lines)
exchanges lines. They work like M-t except in determining the
division of the text into syntactic units.
A numeric argument to a transpose command serves as a repeat count: it tells the transpose command to move the character (word, sexp, line) before or containing point across several other characters (words, sexps, lines). For example, C-u 3 C-t moves the character before point forward across three other characters. This is equivalent to repeating C-t three times. C-u - 4 M-t moves the word before point backward across four words. C-u - C-M-t would cancel the effect of plain C-M-t.
A numeric argument of zero is assigned a special meaning (because otherwise a command with a repeat count of zero would do nothing): to transpose the character (word, sexp, line) ending after point with the one ending after the mark.
A very common error is to type words in the wrong case. Because of this, the word case-conversion commands M-l, M-u and M-c have a special feature when used with a negative argument: they do not move the cursor. As soon as you see you have mistyped the last word, you can simply case-convert it and go on typing. See section Case Conversion Commands.
spell-word).
To check the spelling of the word before point, and optionally correct it
as well, use the command M-$ (spell-word). This command runs
an inferior process containing the spell program to see whether the
word is correct English. If it is not, it asks you to edit the word (in
the minibuffer) into a corrected spelling, and then does a query-replace
to substitute the corrected spelling for the old one throughout the buffer.
If you exit the minibuffer without altering the original spelling, it
means you do not want to do anything to that word. Then the query-replace
is not done.
M-x spell-buffer checks each word in the buffer the same way that
spell-word does, doing a query-replace if appropriate for
every incorrect word.
M-x spell-region is similar but operates only on the region, not the entire buffer.
M-x spell-string reads a string as an argument and checks whether that is a correctly spelled English word. It prints in the echo area a message giving the answer.
The basic unit of stored data in Unix is the file. To edit a file, you must tell Emacs to examine the file and prepare a buffer containing a copy of the file's text. This is called visiting the file. Editing commands apply directly to text in the buffer; that is, to the copy inside Emacs. Your changes appear in the file itself only when you save the buffer back into the file.
In addition to visiting and saving files, Emacs can delete, copy, rename, and append to files, and operate on file directories.
Most Emacs commands that operate on a file require you to specify the file name. (Saving and reverting are exceptions; the buffer knows which file name to use for them.) File names are specified using the minibuffer (see section The Minibuffer). Completion is available, to make it easier to specify long file names. See section Completion.
There is always a default file name which will be used if you type just RET, entering an empty argument. Normally the default file name is the name of the file visited in the current buffer; this makes it easy to operate on that file with any of the Emacs file commands.
Each buffer has a default directory, normally the same as the directory
of the file visited in that buffer. When Emacs reads a file name, if you
do not specify a directory, the default directory is used. If you specify
a directory in a relative fashion, with a name that does not start with a
slash, it is interpreted with respect to the default directory. The
default directory is kept in the variable default-directory, which
has a separate value in every buffer.
For example, if the default file name is `/u/rms/gnu/gnu.tasks' then the default directory is `/u/rms/gnu/'. If you type just `foo', which does not specify a directory, it is short for `/u/rms/gnu/foo'. `../.login' would stand for `/u/rms/.login'. `new/foo' would stand for the filename `/u/rms/gnu/new/foo'.
The command M-x pwd prints the current buffer's default directory,
and the command M-x cd sets it (to a value read using the
minibuffer). A buffer's default directory changes only when the cd
command is used. A file-visiting buffer's default directory is initialized
to the directory of the file that is visited there. If a buffer is made
randomly with C-x b, its default directory is copied from that of the
buffer that was current at the time.
The default directory actually appears in the minibuffer when the
minibuffer becomes active to read a file name. This serves two purposes:
it shows you what the default is, so that you can type a relative file name
and know with certainty what it will mean, and it allows you to edit the
default to specify a different directory. This insertion of the default
directory is inhibited if the variable insert-default-directory is
set to nil.
Note that it is legitimate to type an absolute file name after you enter the minibuffer, ignoring the presence of the default directory name as part of the text. The final minibuffer contents may look invalid, but that is not so. See section Minibuffers for File Names.
`$' in a file name is used to substitute environment variables. For example, if you have used the shell command `setenv FOO rms/hacks' to set up an environment variable named `FOO', then you can use `/u/$FOO/test.c' or `/u/${FOO}/test.c' as an abbreviation for `/u/rms/hacks/test.c'. The environment variable name consists of all the alphanumeric characters after the `$'; alternatively, it may be enclosed in braces after the `$'. Note that the `setenv' command affects Emacs only if done before Emacs is started.
To access a file with `$' in its name, type `$$'. This pair
is converted to a single `$' at the same time as variable substitution
is performed for single `$'. The Lisp function that performs the
substitution is called substitute-in-file-name. The substitution
is performed only on filenames read as such using the minibuffer.
find-file).
find-alternate-file).
find-file-other-window). Don't
change this window.
Visiting a file means copying its contents into Emacs where you can edit them. Emacs makes a new buffer for each file that you visit. We say that the buffer is visiting the file that it was created to hold. Emacs constructs the buffer name from the file name by throwing away the directory, keeping just the name proper. For example, a file named `/usr/rms/emacs.tex' would get a buffer named `emacs.tex'. If there is already a buffer with that name, a unique name is constructed by appending `<2>', `<3>', or so on, using the lowest number that makes a name that is not already in use.
Each window's mode line shows the name of the buffer that is being displayed in that window, so you can always tell what buffer you are editing.
The changes you make with Emacs are made in the Emacs buffer. They do not take effect in the file that you visited, or any place permanent, until you save the buffer. Saving the buffer means that Emacs writes the current contents of the buffer into its visited file. See section Saving Files.
If a buffer contains changes that have not been saved, the buffer is said to be modified. This is important because it implies that some changes will be lost if the buffer is not saved. The mode line displays two stars near the left margin if the buffer is modified.
To visit a file, use the command C-x C-f (find-file). Follow
the command with the name of the file you wish to visit, terminated by a
RET.
The file name is read using the minibuffer (see section The Minibuffer), with defaulting and completion in the standard manner (see section File Names). While in the minibuffer, you can abort C-x C-f by typing C-g.
Your confirmation that C-x C-f has completed successfully is the appearance of new text on the screen and a new buffer name in the mode line. If the specified file does not exist and could not be created, or cannot be read, then an error results. The error message is printed in the echo area, and includes the file name which Emacs was trying to visit.
If you visit a file that is already in Emacs, C-x C-f does not make another copy. It selects the existing buffer containing that file. However, before doing so, it checks that the file itself has not changed since you visited or saved it last. If the file has changed, a warning message is printed. See section Protection against Simultaneous Editing.
What if you want to create a file? Just visit it. Emacs prints `(New File)' in the echo area, but in other respects behaves as if you had visited an existing empty file. If you make any changes and save them, the file is created.
If you visit a nonexistent file unintentionally (because you typed the
wrong file name), use the C-x C-v (find-alternate-file)
command to visit the file you wanted. C-x C-v is similar to C-x
C-f, but it kills the current buffer (after first offering to save it if
it is modified). C-x C-v is allowed even if the current buffer
is not visiting a file.
If the file you specify is actually a directory, Dired is called on that
directory (see section Dired, the Directory Editor). This can be inhibited by setting the variable
find-file-run-dired to nil; then it is an error to try to
visit a directory.
C-x 4 f (find-file-other-window) is like C-x C-f
except that the buffer containing the specified file is selected in another
window. The window that was selected before C-x 4 f continues to
show the same buffer it was already showing. If this command is used when
only one window is being displayed, that window is split in two, with one
window showing the same before as before, and the other one showing the
newly requested file. See section Multiple Windows.
There are two hook variables that allow extensions to modify the
operation of visiting files. Visiting a file that does not exist runs the
functions in the list find-file-not-found-hooks; the value of this
variable is expected to be a list of functions, and the functions are
called one by one until one of them returns non-nil. Any visiting
of a file, whether extant or not, expects find-file-hooks to
contain list of functions and calls them all, one by one. In both cases
the functions receive no arguments. Visiting a nonexistent file
runs the find-file-not-found-hooks first.
Saving a buffer in Emacs means writing its contents back into the file that was visited in the buffer.
save-buffer).
save-some-buffers).
not-modified).
write-file).
When you wish to save the file and make your changes permanent, type
C-x C-s (save-buffer). After saving is finished, C-x C-s
prints a message such as
Wrote /u/rms/gnu/gnu.tasks
If the selected buffer is not modified (no changes have been made in it since the buffer was created or last saved), saving is not really done, because it would have no effect. Instead, C-x C-s prints a message in the echo area saying
(No changes need to be written)
The command C-x s (save-some-buffers) can save any or all modified
buffers. First it asks, for each modified buffer, whether to save it.
These questions should be answered with y or n. C-x C-c,
the key that kills Emacs, invokes save-some-buffers and therefore
asks the same questions.
If you have changed a buffer and do not want the changes to be saved, you
should take some action to prevent it. Otherwise, each time you use
save-some-buffers you are liable to save it by mistake. One thing
you can do is type M-~ (not-modified), which clears out the
indication that the buffer is modified. If you do this, none of the save
commands will believe that the buffer needs to be saved. (`~' is often
used as a mathematical symbol for `not'; thus Meta-~ is `not', metafied.)
You could also use set-visited-file-name (see below) to mark the
buffer as visiting a different file name, one which is not in use for
anything important. Alternatively, you can undo all the changes made since
the file was visited or saved, by reading the text from the file again.
This is called reverting. See section Reverting a Buffer. You could also undo all
the changes by repeating the undo command C-x u until you have undone
all the changes; but this only works if you have not made more changes than
the undo mechanism can remember.
M-x set-visited-file-name alters the name of the file that the
current buffer is visiting. It reads the new file name using the
minibuffer. It can be used on a buffer that is not visiting a file, too.
The buffer's name is changed to correspond to the file it is now visiting
in the usual fashion (unless the new name is in use already for some other
buffer; in that case, the buffer name is not changed).
set-visited-file-name does not save the buffer in the newly visited
file; it just alters the records inside Emacs so that, if you save the
buffer, it will be saved in that file. It also marks the buffer as
"modified" so that C-x C-s will save.
If you wish to mark the buffer as visiting a different file and save it
right away, use C-x C-w (write-file). It is precisely
equivalent to set-visited-file-name followed by C-x C-s.
C-x C-s used on a buffer that is not visiting with a file has the
same effect as C-x C-w; that is, it reads a file name, marks the
buffer as visiting that file, and saves it there. The default file name in
a buffer that is not visiting a file is made by combining the buffer name
with the buffer's default directory.
If Emacs is about to save a file and sees that the date of the latest version on disk does not match what Emacs last read or wrote, Emacs notifies you of this fact, because it probably indicates a problem caused by simultaneous editing and requires your immediate attention. See section Protection against Simultaneous Editing.
If the variable require-final-newline is non-nil, Emacs
puts a newline at the end of any file that doesn't already end in one,
every time a file is saved or written.
You can implement other ways to write files, and other things to be done
before writing them, using the hook variable write-file-hooks. The
value of this variable should be a list of Lisp functions. When a file is
to be written, the functions in the list are called, one by one, with no
arguments. If one of them returns a non-nil value, Emacs takes this
to mean that the file has been written in some suitable fashion; the rest
of the functions are not called, and normal writing is not done.
Because Unix does not provide version numbers in file names, rewriting a
file in Unix automatically destroys all record of what the file used to
contain. Thus, saving a file from Emacs throws away the old contents of
the file--or it would, except that Emacs carefully copies the old contents
to another file, called the backup file, before actually saving.
(Provided the variable make-backup-files is non-nil.
Backup files are not written if this variable is nil).
At your option, Emacs can keep either a single backup file or a series of numbered backup files for each file that you edit.
Emacs makes a backup for a file only the first time the file is saved from one buffer. No matter how many times you save a file, its backup file continues to contain the contents from before the file was visited. Normally this means that the backup file contains the contents from before the current editing session; however, if you kill the buffer and then visit the file again, a new backup file will be made by the next save.
If you choose to have a single backup file (this is the default), the backup file's name is constructed by appending `~' to the file name being edited; thus, the backup file for `eval.c' would be `eval.c~'.
If you choose to have a series of numbered backup files, backup file names are made by appending `.~', the number, and another `~' to the original file name. Thus, the backup files of `eval.c' would be called `eval.c.~1~', `eval.c.~2~', and so on, through names like `eval.c.~259~' and beyond.
If protection stops you from writing backup files under the usual names, the backup file is written as `%backup%~' in your home directory. Only one such file can exist, so only the most recently made such backup is available.
The choice of single backup or numbered backups is controlled by the
variable version-control. Its possible values are
t
nil
never
version-control may be set locally in an individual buffer to
control the making of backups for that buffer's file. For example,
Rmail mode locally sets version-control to never to make sure
that there is only one backup for an Rmail file. See section Local Variables.
To prevent unlimited consumption of disk space, Emacs can delete numbered
backup versions automatically. Generally Emacs keeps the first few backups
and the latest few backups, deleting any in between. This happens every
time a new backup is made. The two variables that control the deletion are
kept-old-versions and kept-new-versions. Their values are, respectively
the number of oldest (lowest-numbered) backups to keep and the number of
newest (highest-numbered) ones to keep, each time a new backup is made.
Recall that these values are used just after a new backup version is made;
that newly made backup is included in the count in kept-new-versions.
By default, both variables are 2.
If trim-versions-without-asking is non-nil, the excess
middle versions are deleted without a murmur. If it is nil, the
default, then you are asked whether the excess middle versions should
really be deleted.
Dired's . (Period) command can also be used to delete old versions. See section Dired, the Directory Editor.
Backup files can be made by copying the old file or by renaming it. This makes a difference when the old file has multiple names. If the old file is renamed into the backup file, then the alternate names become names for the backup file. If the old file is copied instead, then the alternate names remain names for the file that you are editing, and the contents accessed by those names will be the new contents.
The method of making a backup file may also affect the file's owner and group. If copying is used, these do not change. If renaming is used, you become the file's owner, and the file's group becomes the default (different operating systems have different defaults for the group).
Having the owner change is usually a good idea, because then the owner
always shows who last edited the file. Also, the owners of the backups
show who produced those versions. Occasionally there is a file whose
owner should not change; it is a good idea for such files to contain
local variable lists to set backup-by-copying-when-mismatch for
them alone (see section Local Variables in Files).
The choice of renaming or copying is controlled by three variables.
Normally, renaming is done. If the variable backup-by-copying is
non-nil, copying is used. Otherwise, if the variable
backup-by-copying-when-linked is non-nil, then copying is
done for files that have multiple names, but renaming may still done when
the file being edited has only one name. If the variable
backup-by-copying-when-mismatch is non-nil, then copying is
done if renaming would cause the file's owner or group to change.
Simultaneous editing occurs when two users visit the same file, both make changes, and then both save them. If nobody were informed that this was happening, whichever user saved first would later find that his changes were lost. On some systems, Emacs notices immediately when the second user starts to change the file, and issues an immediate warning. When this is not possible, or if the second user has gone on to change the file despite the warning, Emacs checks later when the file is saved, and issues a second warning when a user is about to overwrite a file containing another user's changes. If the editing user takes the proper corrective action at this point, he can prevent actual loss of work.
When you make the first modification in an Emacs buffer that is visiting
a file, Emacs records that you have locked the file. (It does this by
writing another file in a directory reserved for this purpose.) The lock
is removed when you save the changes. The idea is that the file is locked
whenever the buffer is modified. If you begin to modify the buffer while
the visited file is locked by someone else, this constitutes a collision,
and Emacs asks you what to do. It does this by calling the Lisp function
ask-user-about-lock, which you can redefine for the sake of
customization. The standard definition of this function asks you a
question and accepts three possible answers:
file-locked) and the modification you
were trying to make in the buffer does not actually take place.
Note that locking works on the basis of a file name; if a file has multiple names, Emacs does not realize that the two names are the same file and cannot prevent two user from editing it simultaneously under different names. However, basing locking on names means that Emacs can interlock the editing of new files that will not really exist until they are saved.
Some systems are not configured to allow Emacs to make locks. On these systems, Emacs cannot detect trouble in advance, but it still can detect it in time to prevent you from overwriting someone else's changes.
Every time Emacs saves a buffer, it first checks the last-modification date of the existing file on disk to see that it has not changed since the file was last visited or saved. If the date does not match, it implies that changes were made in the file in some other way, and these changes are about to be lost if Emacs actually does save. To prevent this, Emacs prints a warning message and asks for confirmation before saving. Occasionally you will know why the file was changed and know that it does not matter; then you can answer yes and proceed. Otherwise, you should cancel the save with C-g and investigate the situation.
The first thing you should do when notified that simultaneous editing has
already taken place is to list the directory with C-u C-x C-d
(see section Listing a File Directory). This will show the file's current
author. You should attempt to contact him to warn him not to continue
editing. Often the next step is to save the contents of your Emacs buffer
under a different name, and use diff to compare the two
files.
Simultaneous editing checks are also made when you visit with C-x C-f a file that is already visited and when you start to modify a file. This is not strictly necessary, but it can cause you to find out about the problem earlier, when perhaps correction takes less work.
If you have made extensive changes to a file and then change your mind about them, you can get rid of them by reading in the previous version of the file. To do this, use M-x revert-buffer, which operates on the current buffer. Since this is a very dangerous thing to do, you must confirm it with yes.
If the current buffer has been auto-saved more recently than it has been
saved for real, revert-buffer offers to read the auto save file
instead of the visited file (see section Auto-Saving: Protection Against Disasters). This question comes
before the usual request for confirmation, and demands y or n
as an answer. If you have started to type yes for confirmation
without realizing that the other question was going to be asked, the
y will answer that question, but the es will not be valid
confirmation. So you will have a chance to cancel the operation with
C-g and try it again with the answers that you really intend.
revert-buffer keeps point at the same distance (measured in
characters) from the beginning of the file. If the file was edited only
slightly, you will be at approximately the same piece of text after
reverting as before. If you have made drastic changes, the same value of
point in the old file may address a totally different piece of text.
A buffer reverted from its visited file is marked "not modified" until another change is made.
Some kinds of buffers whose contents reflect data bases other than files,
such as Dired buffers, can also be reverted. For them, reverting means
recalculating their contents from the appropriate data base. Buffers
created randomly with C-x b cannot be reverted; revert-buffer
reports an error when asked to do so.
Emacs saves all the visited files from time to time (based on counting your keystrokes) without being asked. This is called auto-saving. It prevents you from losing more than a limited amount of work if the system crashes.
When Emacs determines that it is time for auto-saving, each buffer is considered, and is auto-saved if auto-saving is turned on for it and it has been changed since the last time it was auto-saved. If any auto-saving is done, the message `Auto-saving...' is displayed in the echo area until auto-saving is finished. Errors occurring during auto-saving are caught so that they do not interfere with the execution of commands you have been typing.
Auto-saving does not normally save in the files that you visited, because it can be very undesirable to save a program that is in an inconsistent state when you have made half of a planned change. Instead, auto-saving is done in a different file called the auto-save file, and the visited file is changed only when you request saving explicitly (such as with C-x C-s).
Normally, the auto-save file name is made by appending `#' to the
front and rear of the visited file name. Thus, a buffer visiting file
`foo.c' would be auto-saved in a file `#foo.c#'. Most buffers
that are not visiting files are auto-saved only if you request it
explicitly; when they are auto-saved, the auto-save file name is made by
appending `#%' to the front and `#' to the rear of buffer name.
For example, the `*mail*' buffer in which you compose messages to be
sent is auto-saved in a file named `#%*mail*#'. Auto-save file names
are made this way unless you reprogram parts of Emacs to do something
different (the functions make-auto-save-file-name and
auto-save-file-name-p). The file name to be used for auto-saving
in a buffer is calculated when auto-saving is turned on in that buffer.
If you want auto-saving to be done in the visited file, set the variable
auto-save-visited-file-name to be non-nil. In this mode,
there is really no difference between auto-saving and explicit saving.
A buffer's auto-save file is deleted when you save the buffer in its
visited file. To inhibit this, set the variable delete-auto-save-files
to nil. Changing the visited file name with C-x C-w or
set-visited-file-name renames any auto-save file to go with
the new visited name.
Each time you visit a file, auto-saving is turned on for that file's
buffer if the variable auto-save-default is non-nil (but not
in batch mode; see section Entering and Exiting Emacs). The default for this variable is
t, so auto-saving is the usual practice for file-visiting buffers.
Auto-saving can be turned on or off for any existing buffer with the
command M-x auto-save-mode. Like other minor mode commands, M-x
auto-save-mode turns auto-saving on with a positive argument, off with a
zero or negative argument; with no argument, it toggles.
Emacs does auto-saving periodically based on counting how many characters
you have typed since the last time auto-saving was done. The variable
auto-save-interval specifies how many characters there are between
auto-saves. By default, it is 300. Emacs also auto-saves whenever you
call the function do-auto-save.
Emacs also does auto-saving whenever it gets a fatal error. This
includes killing the Emacs job with a shell command such as kill
%emacs, or disconnecting a phone line or network connection.
The way to use the contents of an auto-save file to recover from a loss of data is with the command M-x recover-file RET file RET. This visits file and then (after your confirmation) restores the contents from from its auto-save file `#file#'. You can then save with C-x C-s to put the recovered text into file itself. For example, to recover file `foo.c' from its auto-save file `#foo.c#', do:
M-x recover-file RET foo.c RET C-x C-s
Before asking for confirmation, M-x recover-file displays a directory listing describing the specified file and the auto-save file, so you can compare their sizes and dates. If the auto-save file is older, M-x recover-file does not offer to read it.
Auto-saving is disabled by M-x recover-file because using this command implies that the auto-save file contains valuable data from a past session. If you save the data in the visited file and then go on to make new changes, you should turn auto-saving back on with M-x auto-save-mode.
Files are classified by Unix into directories. A directory listing is a list of all the files in a directory. Emacs provides directory listings in brief format (file names only) and verbose format (sizes, dates, and authors included).
list-directory).
The command to print a directory listing is C-x C-d (list-directory).
It reads using the minibuffer a file name which is either a directory to be
listed or a wildcard-containing pattern for the files to be listed. For
example,
C-x C-d /u2/emacs/etc RET
lists all the files in directory `/u2/emacs/etc'. An example of specifying a file name pattern is
C-x C-d /u2/emacs/src/*.c RET
Normally, C-x C-d prints a brief directory listing containing just
file names. A numeric argument (regardless of value) tells it to print a
verbose listing (like ls -l).
The text of a directory listing is obtained by running ls in an
inferior process. Two Emacs variables control the switches passed to
ls: list-directory-brief-switches is a string giving the
switches to use in brief listings ("-CF" by default), and
list-directory-verbose-switches is a string giving the switches to
use in a verbose listing ("-l" by default).
Dired makes it easy to delete or visit many of the files in a single directory at once. It makes an Emacs buffer containing a listing of the directory. You can use the normal Emacs commands to move around in this buffer, and special Dired commands to operate on the files.
To invoke dired, do C-x d or M-x dired. The command reads a
directory name or wildcard file name pattern as a minibuffer argument just
like the list-directory command, C-x C-d. Where dired
differs from list-directory is in naming the buffer after the
directory name or the wildcard pattern used for the listing, and putting
the buffer into Dired mode so that the special commands of Dired are
available in it. The variable dired-listing-switches is a string
used as an argument to ls in making the directory; this string
must contain `-l'.
To display the Dired buffer in another window rather than in the selected
window, use C-x 4 d (dired-other-window) instead of C-x d.
Once the Dired buffer exists, you can switch freely between it and other Emacs buffers. Whenever the Dired buffer is selected, certain special commands are provided that operate on files that are listed. The Dired buffer is "read-only", and inserting text in it is not useful, so ordinary printing characters such as d and x are used for Dired commands. Most Dired commands operate on the file described by the line that point is on. Some commands perform operations immediately; others "flag" the file to be operated on later.
Most Dired commands that operate on the current line's file also treat a numeric argument as a repeat count, meaning to act on the files of the next few lines. A negative argument means to operate on the files of the preceding lines, and leave point on the first of those lines.
All the usual Emacs cursor motion commands are available in Dired buffers. Some special purpose commands are also provided. The keys C-n and C-p are redefined so that they try to position the cursor at the beginning of the filename on the line, rather than at the beginning of the line.
For extra convenience, SPC and n in Dired are equivalent to C-n. p is equivalent to C-p. Moving by lines is done so often in Dired that it deserves to be easy to type. DEL (move up and unflag) is often useful simply for moving up.
The g command in Dired runs revert-buffer to reinitialize
the buffer from the actual disk directory and show any changes made in the
directory by programs other than Dired. All deletion flags in the Dired
buffer are lost when this is done.
The primary use of Dired is to flag files for deletion and then delete them.
You can flag a file for deletion by moving to the line describing the file and typing d or C-d. The deletion flag is visible as a `D' at the beginning of the line. Point is moved to the beginning of the next line, so that repeated d commands flag successive files.
The files are flagged for deletion rather than deleted immediately to avoid the danger of deleting a file accidentally. Until you direct Dired to delete the flagged files, you can remove deletion flags using the commands u and DEL. u works just like d, but removes flags rather than making flags. DEL moves upward, removing flags; it is like u with numeric argument automatically negated.
To delete the flagged files, type x. This command first displays a list of all the file names flagged for deletion, and requests confirmation with yes. Once you confirm, all the flagged files are deleted, and their lines are deleted from the text of the Dired buffer. The shortened Dired buffer remains selected. If you answer no or quit with C-g, you return immediately to Dired, with the deletion flags still present and no files actually deleted.
The #, ~ and . commands flag many files for deletion, based on their names. These commands are useful precisely because they do not actually delete any files; you can remove the deletion flags from any flagged files that you really wish to keep.
# flags for deletion all files that appear to have been made by auto-saving (that is, files whose names begin and end with `#'). ~ flags for deletion all files that appear to have been made as backups for files that were edited (that is, files whose names end with `~').
. (Period) flags just some of the backup files for deletion: only
numeric backups that are not among the oldest few nor the newest few
backups of any one file. Normally dired-kept-versions (not
kept-new-versions; that applies only when saving) specifies the
number of newest versions of each file to keep, and
kept-old-versions specifies the number of oldest versions to keep.
Period with a positive numeric argument, as in C-u 3 ., specifies the
number of newest versions to keep, overriding dired-kept-versions.
A negative numeric argument overrides kept-old-versions, using minus
the value of the argument to specify the number of oldest versions of each
file to keep.
Some file operations in Dired take place immediately when they are requested.
Emacs has commands for performing many other operations on files. All operate on one file; they do not accept wild card file names.
M-x view-file allows you to scan or read a file by sequential
screenfuls. It reads a file name argument using the minibuffer. After
reading the file into an Emacs buffer, view-file reads and displays
one windowful. You can then type SPC to scroll forward one windowful,
or DEL to scroll backward. Various other commands are provided for
moving around in the file, but none for changing it; type C-h while
viewing for a list of them. They are mostly the same as normal Emacs
cursor motion commands. To exit from viewing, type C-c.
M-x insert-file inserts a copy of the contents of the specified file into the current buffer at point, leaving point unchanged before the contents and the mark after them. See section The Mark and the Region.
M-x write-region is the inverse of M-x insert-file; it copies the contents of the region into the specified file. M-x append-to-file adds the text of the region to the end of the specified file.
M-x delete-file deletes the specified file, like the rm
command in the shell. If you are deleting many files in one directory, it
may be more convenient to use Dired (see section Dired, the Directory Editor).
M-x rename-file reads two file names old and new using the minibuffer, then renames file old as new. If a file named new already exists, you must confirm with yes or renaming is not done; this is because renaming causes the old meaning of the name new to be lost. If old and new are on different file systems, the file old is copied and deleted.
The similar command M-x add-name-to-file is used to add an additional name to an existing file without removing its old name. The new name must belong on the same file system that the file is on.
M-x copy-file reads the file old and writes a new file named new with the same contents. Confirmation is required if a file named new already exists, because copying has the consequence of overwriting the old contents of the file new.
M-x make-symbolic-link reads two file names old and linkname, and then creates a symbolic link named linkname and pointing at old. The effect is that future attempts to open file linkname will refer to whatever file is named old at the time the opening is done, or will get an error if the name old is not in use at that time. Confirmation is required when creating the link if linkname is in use. Note that not all systems support symbolic links.
The text you are editing in Emacs resides in an object called a buffer. Each time you visit a file, a buffer is created to hold the file's text. Each time you invoke Dired, a buffer is created to hold the directory listing. If you send a message with C-x m, a buffer named `*mail*' is used to hold the text of the message. When you ask for a command's documentation, that appears in a buffer called `*Help*'.
At any time, one and only one buffer is selected. It is also called the current buffer. Often we say that a command operates on "the buffer" as if there were only one; but really this means that the command operates on the selected buffer (most commands do).
When Emacs makes multiple windows, each window has a chosen buffer which is displayed there, but at any time only one of the windows is selected and its chosen buffer is the selected buffer. Each window's mode line displays the name of the buffer that the window is displaying (see section Multiple Windows).
Each buffer has a name, which can be of any length, and you can select any buffer by giving its name. Most buffers are made by visiting files, and their names are derived from the files' names. But you can also create an empty buffer with any name you want. A newly started Emacs has a buffer named `*scratch*' which can be used for evaluating Lisp expressions in Emacs. The distinction between upper and lower case matters in buffer names.
Each buffer records individually what file it is visiting, whether it is modified, and what major mode and minor modes are in effect in it (see section Major Modes). Any Emacs variable can be made local to a particular buffer, meaning its value in that buffer can be different from the value in other buffers. See section Local Variables.
switch-to-buffer).
switch-to-buffer-other-window).
To select the buffer named bufname, type C-x b bufname
RET. This is the command switch-to-buffer with argument
bufname. You can use completion on an abbreviation for the buffer
name you want (see section Completion). An empty argument to C-x b
specifies the most recently selected buffer that is not displayed in any
window.
Most buffers are created by visiting files, or by Emacs commands that
want to display some text, but you can also create a buffer explicitly by
typing C-x b bufname RET. This makes a new, empty buffer which
is not visiting any file, and selects it for editing. Such buffers are
used for making notes to yourself. If you try to save one, you are asked
for the file name to use. The new buffer's major mode is determined by the
value of default-major-mode (see section Major Modes).
Note that C-x C-f, and any other command for visiting a file, can also be used to switch buffers. See section Visiting Files.
list-buffers).
To print a list of all the buffers that exist, type C-x C-b. Each line in the list shows one buffer's name, major mode and visited file. `*' at the beginning of a line indicates the buffer is "modified". If several buffers are modified, it may be time to save some with C-x s (see section Saving Files). `%' indicates a read-only buffer. `.' marks the selected buffer. Here is an example of a buffer list:
MR Buffer Size Mode File
-- ------ ---- ---- ----
.* emacs.tex 383402 Texinfo /u2/emacs/man/emacs.tex
*Help* 1287 Fundamental
files.el 23076 Emacs-Lisp /u2/emacs/lisp/files.el
% RMAIL 64042 RMAIL /u/rms/RMAIL
*% man 747 Dired
net.emacs 343885 Fundamental /u/rms/net.emacs
fileio.c 27691 C /u2/emacs/src/fileio.c
NEWS 67340 Text /u2/emacs/etc/NEWS
*scratch* 0 Lisp Interaction
Note that the buffer `*Help*' was made by a help request; it is not
visiting any file. The buffer man was made by Dired on the
directory `/u2/emacs/man/'.
toggle-read-only).
A buffer can be read-only, which means that commands to change its
text are not allowed. Normally, read-only buffers are made by subsystems
such as Dired and Rmail that have special commands to operate on the text;
a read-only buffer is also made if you visit a file that is protected so
you cannot write it. If you wish to make changes in a read-only buffer,
use the command C-x C-q (toggle-read-only). It makes a
read-only buffer writable, and makes a writable buffer read-only. This
works by setting the variable buffer-read-only, which has a local
value in each buffer and makes the buffer read-only if its value is
non-nil.
M-x rename-buffer changes the name of the current buffer. Specify the new name as a minibuffer argument. There is no default. If you specify a name that is in use for some other buffer, an error happens and no renaming is done.
M-x view-buffer is much like M-x view-file (see section Miscellaneous File Operations) except that it examines an already existing Emacs buffer. View mode provides commands for scrolling through the buffer conveniently but not for changing it. When you exit View mode, the value of point that resulted from your perusal remains in effect.
The commands C-x a (append-to-buffer) and M-x
insert-buffer can be used to copy text from one buffer to another.
See section Accumulating Text.
After you use Emacs for a while, you may accumulate a large number of buffers. You may then find it convenient to eliminate the ones you no longer need. There are several commands provided for doing this.
kill-buffer).
C-x k (kill-buffer) kills one buffer, whose name you specify
in the minibuffer. The default, used if you type just RET in the
minibuffer, is to kill the current buffer. If the current buffer is
killed, another buffer is selected; a buffer that has been selected
recently but does not appear in any window now is chosen to be selected.
If the buffer being killed is modified (has unsaved editing) then you are
asked to confirm with yes before the buffer is killed.
The command M-x kill-some-buffers asks about each buffer, one by
one. An answer of y means to kill the buffer. Killing the current
buffer or a buffer containing unsaved changes selects a new buffer or asks
for confirmation just like kill-buffer.
The buffer-menu facility is like a "Dired for buffers"; it allows you to request operations on various Emacs buffers by editing an Emacs buffer containing a list of them. You can save buffers, kill them (here called deleting them, for consistency with Dired), or display them.
The command buffer-menu writes a list of all Emacs buffers into
the buffer `*Buffer List*', and selects that buffer in Buffer Menu
mode. The buffer is read-only, and can only be changed through the special
commands described in this section. Most of these commands are graphic
characters. The usual Emacs cursor motion commands can be used in the
`*Buffer List*' buffer. The following special commands apply to the
buffer described on the current line.
All the commands that put in or remove flags to request later operations also move down a line, and accept a numeric argument as a repeat count, unless otherwise specified.
There are also special commands to use the buffer list to select another buffer, and to specify one or more other buffers for display in additional windows.
All that buffer-menu does directly is create and select a suitable
buffer, and turn on Buffer Menu mode. Everything else described above is
implemented by the special commands provided in Buffer Menu mode. One
consequence of this is that you can switch from the `*Buffer List*'
buffer to another Emacs buffer, and edit there. You can reselect the
buffer-menu buffer later, to perform the operations already
requested, or you can kill it, or pay no further attention to it.
The only difference between buffer-menu and list-buffers is
that buffer-menu selects the `*Buffer List*' buffer and
list-buffers does not. If you run list-buffers (that is,
type C-x C-b) and select the buffer list manually, you can use all of
the commands described here.
Emacs can split the screen into two or many windows, which can display parts of different buffers, or different parts of one buffer.
When multiple windows are being displayed, each window has an Emacs buffer designated for display in it. The same buffer may appear in more than one window; if it does, any changes in its text are displayed in all the windows where it appears. But the windows showing the same buffer can show different parts of it, because each window has its own value of point.
At any time, one of the windows is the selected window; the buffer this window is displaying is the current buffer. The terminal's cursor shows the location of point in this window. Each other window has a location of point as well, but since the terminal has only one cursor there is no way to show where those locations are.
Commands to move point affect the value of point for the selected Emacs
window only. They do not change the value of point in any other Emacs
window, even one showing the same buffer. The same is true for commands
such as C-x b to change the selected buffer in the selected window;
they do not affect other windows at all. However, there are other commands
such as C-x 4 b that select a different window and switch buffers in
it. Also, all commands that display information in a window, including
(for example) C-h f (describe-function) and C-x C-b
(list-buffers), work by switching buffers in a nonselected window
without affecting the selected window.
Each window has its own mode line, which displays the buffer name, modification status and major and minor modes of the buffer that is displayed in the window. See section The Mode Line, for full details on the mode line.
split-window-vertically).
split-window-horizontally).
The command C-x 2 (split-window-vertically) breaks the
selected window into two windows, one above the other. Both windows start
out displaying the same buffer, with the same value of point. By default
the two windows each get half the height of the window that was split; a
numeric argument specifies how many lines to give to the top window.
C-x 5 (split-window-horizontally) breaks the selected
window into two side-by-side windows. A numeric argument specifies
how many columns to give the one on the left. A line of vertical bars
separates the two windows. Windows that are not the full width of the
screen have mode lines, but they are truncated; also, they do not
always appear in inverse video, because, the Emacs display routines
have not been taught how to display a region of inverse video that is
only part of a line on the screen.
When a window is less than the full width, text lines too long to fit are
frequent. Continuing all those lines might be confusing. The variable
truncate-partial-width-windows can be set non-nil to force
truncation in all windows less than the full width of the screen,
independent of the buffer being displayed and its value for
truncate-lines. See section Continuation Lines.
Horizontal scrolling is often used in side-by-side windows. See section Controlling the Display.
other-window). That is o, not zero.
scroll-other-window).
To select a different window, use C-x o (other-window).
That is an o, for `other', not a zero. When there are more than two
windows, this command moves through all the windows in a cyclic order,
generally top to bottom and left to right. From the rightmost and
bottommost window, it goes back to the one at the upper left corner. A
numeric argument means to move several steps in the cyclic order of
windows. A negative argument moves around the cycle in the opposite order.
When the minibuffer is active, the minibuffer is the last window in the
cycle; you can switch from the minibuffer window to one of the other
windows, and later switch back and finish supplying the minibuffer argument
that is requested. See section Editing in the Minibuffer.
The usual scrolling commands (see section Controlling the Display) apply to the selected
window only, but there is one command to scroll the next window.
C-M-v (scroll-other-window) scrolls the window that C-x o
would select. It takes arguments, positive and negative, like C-v.
The command M-x compare-windows compares the text in the current window with that in the next window. Comparison starts at point in each window. Point moves forward in each window, a character at a time in each window, until the next characters in the two windows are different. Then the command is finished.
C-x 4 is a prefix key for commands that select another window (splitting the window if there is only one) and select a buffer in that window. Different C-x 4 commands have different ways of finding the buffer to select.
switch-to-buffer-other-window.
find-file-other-window. See section Visiting Files.
dired-other-window. See section Dired, the Directory Editor.
mail-other-window, and its same-window version is C-x m
(see section Sending Mail).
find-tag-other-window, the multiple-window variant of M-.
(see section Tag Tables).
kill-window). That is a zero.
delete-other-windows).
enlarge-window).
enlarge-window-horizontally).
To delete a window, type C-x 0 (delete-window). (That is a
zero.) The space occupied by the deleted window is distributed among the
other active windows (but not the minibuffer window, even if that is active
at the time). Once a window is deleted, its attributes are forgotten;
there is no automatic way to make another window of the same shape or
showing the same buffer. But the buffer continues to exist, and you can
select it in any window with C-x b.
C-x 1 (delete-other-windows) is more powerful than C-x 0;
it deletes all the windows except the selected one (and the minibuffer);
the selected window expands to use the whole screen except for the echo
area.
To readjust the division of space among existing windows, use C-x ^
(enlarge-window). It makes the currently selected window get one
line bigger, or as many lines as is specified with a numeric argument.
With a negative argument, it makes the selected window smaller. C-x
} (enlarge-window-horizontally) makes the selected window wider
by the specified number of columns. The extra screen space given to a
window comes from one of its neighbors, if that is possible; otherwise, all
the competing windows are shrunk in the same proportion. If this makes any
windows too small, those windows are deleted and their space is divided up.
The minimum size is specified by the variables window-min-height and
window-min-width.
Emacs has many different major modes, each of which customizes Emacs for editing text of a particular sort. The major modes are mutually exclusive, and each buffer has one major mode at any time. The mode line normally contains the name of the current major mode, in parentheses. See section The Mode Line.
The least specialized major mode is called Fundamental mode. This mode has no mode-specific redefinitions or variable settings, so that each Emacs command behaves in its most general manner, and each option is in its default state. For editing any specific type of text, such as Lisp code or English text, you should switch to the appropriate major mode, such as Lisp mode or Text mode.
Selecting a major mode changes the meanings of a few keys to become more specifically adapted to the language being edited. The ones which are changed frequently are TAB, DEL, and LFD. In addition, the commands which handle comments use the mode to determine how comments are to be delimited. Many major modes redefine the syntactical properties of characters appearing in the buffer. See section The Syntax Table.
The major modes fall into three major groups. Lisp mode (which has several variants), C mode and Muddle mode are for specific programming languages. Text mode, Nroff mode, TeX mode and Outline mode are for editing English text. The remaining major modes are not intended for use on users' files; they are used in buffers created for specific purposes by Emacs, such as Dired mode for buffers made by Dired (see section Dired, the Directory Editor), and Mail mode for buffers made by C-x m (see section Sending Mail), and Shell mode for buffers used for communicating with an inferior shell process (see section Interactive Inferior Shell).
Most programming language major modes specify that only blank lines separate paragraphs. This is so that the paragraph commands remain useful. See section Paragraphs. They also cause Auto Fill mode to use the definition of TAB to indent the new lines it creates. This is because most lines in a program are usually indented. See section Indentation.
You can select a major mode explicitly for the current buffer, but most of the time Emacs determines which mode to use based on the file name or some text in the file.
Explicit selection of a new major mode is done with a M-x command.
From the name of a major mode, add -mode to get the name of a
command to select that mode. Thus, you can enter Lisp mode by executing
M-x lisp-mode.
When you visit a file, Emacs usually chooses the right major mode based
on the file's name. For example, files whose names end in .c are
edited in C mode. The correspondence between file names and major mode is
controlled by the variable auto-mode-alist. Its value is a list in
which each element has the form
(regexp . mode-function)
For example, one element normally found in the list has the form
("\\.c$" . c-mode), and it is responsible for selecting C mode
for files whose names end in `.c'. (Note that `\\' is needed in
Lisp syntax to include a `\' in the string, which is needed to
suppress the special meaning of `.' in regexps.) The only practical
way to change this variable is with Lisp code.
You can specify which major mode should be used for editing a certain file by a special sort of text in the first nonblank line of the file. The mode name should appear in this line both preceded and followed by `-*-'. Other text may appear on the line as well. For example,
;-*-Lisp-*-
tells Emacs to use Lisp mode. Note how the semicolon is used to make Lisp treat this line as a comment. Such an explicit specification overrides any defaulting based on the file name.
Another format of mode specification is
-*-Mode: modename;-*-
which allows other things besides the major mode name to be specified. However, Emacs does not look for anything except the mode name.
The major mode can also be specified in a local variables list. See section Local Variables in Files.
When a file is visited that does not specify a major mode to use, or when
a new buffer is created with C-x b, the major mode used is that
specified by the variable default-major-mode. Normally this value
is the symbol fundamental-mode, which specifies Fundamental mode.
If default-major-mode is nil, the major mode is taken from
the previously selected buffer.
newline-and-indent).
delete-indentation). This would cancel out
the effect of LFD.
split-line).
back-to-indentation).
indent-region).
indent-rigidly).
tab-to-tab-stop).
Most programming languages have some indentation convention. For Lisp code, lines are indented according to their nesting in parentheses. The same general idea is used for C code, though many details are different.
Whatever the language, to indent a line, use the TAB command. Each major mode defines this command to perform the sort of indentation appropriate for the particular language. In Lisp mode, TAB aligns the line according to its depth in parentheses. No matter where in the line you are when you type TAB, it aligns the line as a whole. In C mode, TAB implements a subtle and sophisticated indentation style that knows about many aspects of C syntax.
In Text mode, TAB runs the command tab-to-tab-stop, which
indents to the next tab stop column. You can set the tab stops with
M-x edit-tab-stops.
If you just want to insert a tab character in the buffer, you can type C-q TAB.
To move over the indentation on a line, do Meta-m
(back-to-indentation). This command, given anywhere on a line,
positions point at the first nonblank character on the line.
To insert an indented line before the current line, do C-a C-o TAB. To make an indented line after the current line, use C-e LFD.
C-M-o (split-line) moves the text from point to the end of
the line vertically down, so that the current line becomes two lines.
C-M-o first moves point forward over any spaces and tabs. Then it
inserts after point a newline and enough indentation to reach the same
column point is on. Point remains before the inserted newline; in this
regard, C-M-o resembles C-o.
To join two lines cleanly, use the Meta-^ (delete-indentation)
command to delete the indentation at the front of the current line, and the
line boundary as well. They are replaced by a single space, or by no space
if at the beginning of a line or before a `)' or after a `('. To
delete just the indentation of a line, go to the beginning of the line and
use Meta-\ (delete-horizontal-space), which deletes all spaces
and tabs around the cursor.
There are also commands for changing the indentation of several lines at
once. Control-Meta-\ (indent-region) gives each line which
begins in the region the "usual" indentation by invoking TAB at the
beginning of the line. A numeric argument specifies the column to indent
to, and each line is shifted left or right so that its first nonblank
character appears in that column. C-x TAB
(indent-rigidly) moves all of the lines in the region right by its
argument (left, for negative arguments). The whole group of lines moves
rigidly sideways, which is how the command gets its name.
M-x indent-relative indents at point based on the previous line
(actually, the last nonempty line.) It inserts whitespace at point, moving
point, until it is underneath an indentation point in the previous line.
An indentation point is the end of a sequence of whitespace or the end of
the line. If point is farther right than any indentation point in the
previous line, the whitespace before point is deleted and the first
indentation point then applicable is used. If no indentation point is
applicable even then, tab-to-tab-stop is run (see next section).
indent-relative is the definition of TAB in Indented Text
mode. See section Commands for Human Languages.
For typing in tables, you can use Text mode's definition of TAB,
tab-to-tab-stop. This command inserts indentation before point,
enough to reach the next tab stop column. If you are not in Text mode,
this function can be found on M-i anyway.
The tab stops used by M-i can be set arbitrarily by the user.
They are stored in a variable called tab-stop-list, as a list of
column-numbers in increasing order.
The convenient way to set the tab stops is using M-x edit-tab-stops,
which creates and selects a buffer containing a description of the tab stop
settings. You can edit this buffer to specify different tab stops, and
then type C-c C-c to make those new tab stops take effect. In the
tab stop buffer, C-c C-c runs the function
edit-tab-stops-note-changes rather than its usual definition
save-buffer. edit-tab-stops records which buffer was current
when you invoked it, and stores the tab stops back in that buffer; normally
all buffers share the same tab stops and changing them in one buffer
affects all, but if you happen to make tab-stop-list local in one
buffer then edit-tab-stops in that buffer will edit the local
settings.
Here is what the text representing the tab stops looks like for ordinary tab stops every eight columns.
: : : : : :
0 1 2 3 4
0123456789012345678901234567890123456789012345678
To install changes, type C-c C-c
The first line contains a colon at each tab stop. The remaining lines are present just to help you see where the colons are and know what to do.
Note that the tab stops that control tab-to-tab-stop have nothing
to do with displaying tab characters in the buffer. See section Variables Controlling Display,
for more information on that.
Emacs normally uses both tabs and spaces to indent lines. If you prefer,
all indentation can be made from spaces only. To request this, set
indent-tabs-mode to nil. This is a per-buffer variable;
altering the variable affects only the current buffer, but there is a
default value which you can change as well. See section Local Variables.
There are also commands to convert tabs to spaces or vice versa, always preserving the columns of all nonblank text. M-x tabify scans the region for sequences of spaces, and converts sequences of at least three spaces to tabs if that can be done without changing indentation. M-x untabify changes all tabs in the region to appropriate numbers of spaces.
The term text has two widespread meanings in our area of the computer field. One is data that is a sequence of characters. Any file that you edit with Emacs is text, in this sense of the word. The other meaning is more restrictive: a sequence of characters in a human language for humans to read (possibly after processing by a text formatter), as opposed to a program or commands for a program.
Human languages have syntactic/stylistic conventions that can be supported or used to advantage by editor commands: conventions involving words, sentences, paragraphs, and capital letters. This chapter describes Emacs commands for all of these things. There are also commands for filling, or rearranging paragraphs into lines of approximately equal length. The commands for moving over and killing words, sentences and paragraphs, while intended primarily for editing text, are also often useful for editing programs.
Emacs has several major modes for editing human language text. If the file contains text pure and simple, use Text mode, which customizes Emacs in small ways for the syntactic conventions of text. For text which contains embedded commands for text formatters, Emacs has other major modes, each for a particular text formatter. Thus, for input to TeX, you would use TeX mode; for input to nroff, Nroff mode.
Editing files of text in a human language ought to be done using Text
mode rather than Lisp or Fundamental mode. Invoke M-x text-mode to
enter Text mode. In Text mode, TAB runs the function
tab-to-tab-stop, which allows you to use arbitrary tab stops set
with M-x edit-tab-stops (see section Tab Stops). Features concerned with
comments in programs are turned off except when explicitly invoked. The
syntax table is changed so that periods are not considered part of a word,
while apostrophes, backspaces and underlines are.
A similar variant mode is Indented Text mode, intended for editing text
in which most lines are indented. This mode defines TAB to run
indent-relative (see section Indentation), and makes Auto Fill indent
the lines it creates. The result is that normally a line made by Auto
Filling, or by LFD, is indented just like the previous line. Use
M-x indented-text-mode to select this mode.
Entering Text mode or Indented Text mode calls with no arguments the
value of the variable text-mode-hook, if that value exists and is
not nil. This value is also called when modes related to Text mode
are entered; this includes Nroff mode, TeX mode, Outline mode and Mail
mode. Your hook can look at the value of major-mode to see which of
these modes is actually being entered.
Nroff mode is a mode like Text mode but modified to handle nroff commands present in the text. Invoke M-x nroff-mode to enter this mode. It differs from Text mode in only a few ways. All nroff command lines are considered paragraph separators, so that filling will never garble the nroff commands. Pages are separated by `.bp' commands. Comments start with backslash-doublequote. Also, three special commands are provided that are not in Text mode:
forward-text-line). An argument is a repeat count.
backward-text-line).
count-text-lines).
The other feature of Nroff mode is that you can turn on Electric Nroff newline mode. This is a minor mode that you can turn on or off with M-x electric-nroff-mode (see section Minor Modes). When the mode is on, each time you use RET to end a line that contains an nroff command that opens a kind of grouping, the matching nroff command to close that grouping is automatically inserted on the following line. For example, if you are at the beginning of a line and type . ( b RET, the matching command `.)b' will be inserted on a new line following point.
Entering Nroff mode calls with no arguments the value of the variable
text-mode-hook, if that value exists and is not nil; then it
does the same with the variable nroff-mode-hook.
TeX is a powerful text formatter written by Donald Knuth; it is also free, like GNU Emacs. LaTeX is a simplified input format for TeX, implemented by TeX macros. It comes with TeX.
Emacs has a special TeX mode for editing TeX input files. It provides facilities for checking the balance of delimiters and for invoking TeX on all or part of the file.
TeX mode has two variants, Plain TeX mode and LaTeX mode
(actually two distinct major modes which differ only slightly). They are
designed for editing the two different input formats. The command M-x
tex-mode looks at the contents of the buffer to determine whether the
contents appear to be LaTeX input or not; it then selects the
appropriate mode. If it can't tell which is right (e.g., the buffer is
empty), the variable TeX-default-mode controls which mode is used.
The commands M-x plain-tex-mode and M-x latex-mode explicitly select the two variants of TeX mode. Use these commands when M-x tex-mode does not guess right.
TeX for Unix systems can be obtained from the University of Washington for a distribution fee.
To order a full distribution, send $140.00 for a 1/2 inch 9-track tape, $165.00 for two 4-track 1/4 inch cartridge tapes (foreign sites $150.00, for 1/2 inch, $175.00 for 1/4 inch, to cover the extra postage) payable to the University of Washington to:
The Director Northwest Computer Support Group, DW-10 University of Washington Seattle, Washington 98195
Purchase orders are acceptable, but there is an extra charge of $10.00, to pay for processing charges. (Total of $150 for domestic sites, $175 for foreign sites).
The normal distribution is a tar tape, blocked 20, 1600 bpi, on an industry standard 2400 foot half-inch reel. The physical format for the 1/4 inch streamer cartridges uses QIC-11, 8000 bpi, 4-track serpentine recording for the SUN. Also, SystemV tapes can be written in cpio format, blocked 5120 bytes, ASCII headers.
Here are the special commands provided in TeX mode for editing the text of the file.
TeX-insert-quote).
TeX-terminate-paragraph).
TeX-insert-braces).
up-list).
TeX-close-LaTeX-block).
In TeX, the character `"' is not normally used; one uses `"'
to start a quotation and `"' to end one. TeX mode defines the key
" to insert `"' after whitespace or an open brace, `"'
after a backslash, or `"' otherwise. This is done by the command
TeX-insert-quote. If you need the character `"' itself in
unusual contexts, use C-q to insert it. Also, " with a
numeric argument always inserts that number of `"' characters.
In TeX mode, `$' has a special syntax code which attempts to understand the way TeX math mode delimiters match. When you insert a `$' that is meant to exit math mode, the position of the matching `$' that entered math mode is displayed for a second. This is the same feature that displays the open brace that matches a close brace that is inserted. However, there is no way to tell whether a `$' enters math mode or leaves it; so when you insert a `$' that enters math mode, the previous `$' position is shown as if it were a match, even though they are actually unrelated.
If you prefer to keep braces balanced at all times, you can use M-{
(TeX-insert-braces) to insert a pair of braces. It leaves point
between the two braces so you can insert the text that belongs inside.
Afterward, use the command M-} (up-list) to move forward
past the close brace.
There are two commands for checking the matching of braces. LFD
(TeX-terminate-paragraph) checks the paragraph before point, and
inserts two newlines to start a new paragraph. It prints a message in the
echo area if any mismatch is found. M-x validate-TeX-buffer checks
the entire buffer, paragraph by paragraph. When it finds a paragraph that
contains a mismatch, it displays point at the beginning of the paragraph
for a few seconds and pushes a mark at that spot. Scanning continues
until the whole buffer has been checked or until you type another key.
The positions of the last several paragraphs with mismatches can be
found in the mark ring (see section The Mark Ring).
Note that square brackets and parentheses are matched in TeX mode, not just braces. This is wrong for the purpose of checking TeX syntax. However, parentheses and square brackets are likely to be used in text as matching delimiters and it is useful for the various motion commands and automatic match display to work with them.
In LaTeX input, `\begin' and `\end' commands must balance.
After you insert a `\begin', use C-c C-f
(TeX-close-LaTeX-block) to insert automatically a matching
`\end' (on a new line following the `\begin'). A blank line is
inserted between the two, and point is left there.
You can invoke TeX as an inferior of Emacs on either the entire contents of the buffer or just a region at a time. Running TeX in this way on just one chapter is a good way to see what your changes look like without taking the time to format the entire file.
TeX-region).
TeX-buffer).
TeX-recenter-output-buffer).
TeX-kill-job).
TeX-print).
TeX-show-print-queue).
You can pass the current buffer through an inferior TeX by means of
C-c C-b (TeX-buffer). The formatted output appears in a file
in `/tmp'; to print it, type C-c C-p (TeX-print).
Afterward use C-c C-q (TeX-show-print-queue) to view the
progress of your output towards being printed.
The console output from TeX, including any error messages, appear in a buffer called `*TeX-shell*'. If TeX gets an error, you can switch to this buffer and feed it input (this works as in Shell mode; see section Interactive Inferior Shell). Without switching to this buffer you can scroll it so that its last line is visible by typing C-c C-l.
Type C-c C-k (TeX-kill-job) to kill the TeX process if
you see that its output is no longer useful. Using C-c C-b or
C-c C-r also kills any TeX process still running.
You can also pass an arbitrary region through an inferior TeX by typing
C-c C-r (TeX-region). This is tricky, however, because most files
of TeX input contain commands at the beginning to set parameters and
define macros, without which no later part of the file will format
correctly. To solve this problem, C-c C-r allows you to designate a
part of the file as containing essential commands; it is included before
the specified region as part of the input to TeX. The designated part
of the file is called the header.
To indicate the bounds of the header in Plain TeX mode, you insert two special strings in the file. Insert `%**start of header' before the header, and `%**end of header' after it. Each string must appear entirely on one line, but there may be other text on the line before or after. The lines containing the two strings are included in the header. If `%**start of header' does not appear within the first 100 lines of the buffer, C-c C-r assumes that there is no header.
In LaTeX mode, the header begins with `\documentstyle' and ends with `\begin{document}'. These are commands that LaTeX requires you to use in any case, so nothing special needs to be done to identify the header.
Entering either kind of TeX mode calls with no arguments the value of
the variable text-mode-hook, if that value exists and is not
nil; then it does the same with the variable TeX-mode-hook.
Finally it does the same with either plain-TeX-mode-hook or
LaTeX-mode-hook.
Outline mode is a major mode much like Text mode but intended for editing outlines. It allows you to make parts of the text temporarily invisible so that you can see just the overall structure of the outline. Type M-x outline-mode to turn on Outline mode in the current buffer.
Entering Outline mode calls with no arguments the value of the variable
text-mode-hook, if that value exists and is not nil; then it
does the same with the variable outline-mode-hook.
When a line is invisible in outline mode, it does not appear on the screen. The screen appears exactly as if the invisible line were deleted, except that an ellipsis (three periods in a row) appears at the end of the previous visible line (only one ellipsis no matter how many invisible lines follow).
All editing commands treat the text of the invisible line as part of the previous visible line. For example, C-n moves onto the next visible line. Killing an entire visible line, including its terminating newline, really kills all the following invisible lines along with it; yanking it all back yanks the invisible lines and they remain invisible.
Outline mode assumes that the lines in the buffer are of two types: heading lines and body lines. A heading line represents a topic in the outline. Heading lines start with one or more stars; the number of stars determines the depth of the heading in the outline structure. Thus, a heading line with one star is a major topic; all the heading lines with two stars between it and the next one-star heading are its subtopics; and so on. Any line that is not a heading line is a body line. Body lines belong to the preceding heading line. Here is an example:
* Food This is the body, which says something about the topic of food. ** Delicious Food This is the body of the second-level header. ** Distasteful Food This could have a body too, with several lines. *** Dormitory Food * Shelter A second first-level topic with its header line.
A heading line together with all following body lines is called collectively an entry. A heading line together with all following deeper heading lines and their body lines is called a subtree.
You can customize the criterion for distinguishing heading lines
by setting the variable outline-regexp. Any line whose
beginning has a match for this regexp is considered a heading line.
Matches that start within a line (not at the beginning) do not count.
The length of the matching text determines the level of the heading;
longer matches make a more deeply nested level. Thus, for example,
if a text formatter has commands `@chapter', `@section'
and `@subsection' to divide the document into chapters and
sections, you could make those lines count as heading lines by
setting outline-regexp to `"@chap\\|@\\(sub\\)*section"'.
Note the trick: the two words `chapter' and `section' are equally
long, but by defining the regexp to match only `chap' we ensure
that the length of the text matched on a chapter heading is shorter,
so that Outline mode will know that sections are contained in chapters.
This works as long as no other command starts with `@chap'.
Outline mode makes a line invisible by changing the newline before it into an ASCII Control-M (code 015). Most editing commands that work on lines treat an invisible line as part of the previous line because, strictly speaking, it is part of that line, since there is no longer a newline in between. When you save the file in Outline mode, Control-M characters are saved as newlines, so the invisible lines become ordinary lines in the file. But saving does not change the visibility status of a line inside Emacs.
There are some special motion commands in Outline mode that move backward and forward to heading lines.
outline-next-visible-heading).
outline-previous-visible-heading).
outline-forward-same-level).
outline-backward-same-level).
outline-up-heading).
C-c C-n (next-visible-heading) moves down to the next
heading line. C-c C-p (previous-visible-heading) moves
similarly backward. Both accept numeric arguments as repeat counts. The
names emphasize that invisible headings are skipped, but this is not really
a special feature. All editing commands that look for lines ignore the
invisible lines automatically.
More advanced motion commands understand the levels of headings.
The commands C-c C-f (outline-forward-same-level) and
C-c C-b (outline-backward-same-level) move from one
heading line to another visible heading at the same depth in
the outline. C-c C-u (outline-up-heading) moves
backward to another heading that is less deeply nested.
The other special commands of outline mode are used to make lines visible
or invisible. Their names all start with hide or show.
Most of them fall into pairs of opposites. They are not undoable; instead,
you can undo right past them. Making lines visible or invisible is simply
not recorded by the undo mechanism.
hide-subtree).
show-subtree).
show-children).
Two commands that are exact opposites are M-x hide-entry and M-x show-entry. They are used with point on a heading line, and apply only to the body lines of that heading. The subtopics and their bodies are not affected.
Two more powerful opposites are C-c C-h (hide-subtree) and
C-c C-s (show-subtree). Both expect to be used when point is
on a heading line, and both apply to all the lines of that heading's
subtree: its body, all its subheadings, both direct and indirect, and
all of their bodies. In other words, the subtree contains everything
following this heading line, up to and not including the next heading of
the same or higher rank.
Intermediate between a visible subtree and an invisible one is having all the subheadings visible but none of the body. There are two commands for doing this, depending on whether you want to hide the bodies or make the subheadings visible. They are M-x hide-leaves and M-x show-branches.
A little weaker than show-branches is C-c C-i
(show-children). It makes just the direct subheadings
visible--those one level down. Deeper subheadings remain invisible, if
they were invisible.
Two commands have a blanket effect on the whole file. M-x hide-body makes all body lines invisible, so that you see just the outline structure. M-x show-all makes all lines visible. These commands can be thought of as a pair of opposites even though M-x show-all applies to more than just body lines.
The use of ellipses at the ends of visible lines can be turned off
by setting selective-display-ellipses to nil. Then there
is no visible indication of the presence of invisible lines.
Emacs has commands for moving over or operating on words. By convention, the keys for them are all Meta- characters.
forward-word).
backward-word).
kill-word).
backward-kill-word).
mark-word).
transpose-words).
Notice how these keys form a series that parallels the character-based C-f, C-b, C-d, C-t and DEL. M-@ is related to C-@, which is an alias for C-SPC.
The commands Meta-f (forward-word) and Meta-b
(backward-word) move forward and backward over words. They are thus
analogous to Control-f and Control-b, which move over single
characters. Like their Control- analogues, Meta-f and
Meta-b move several words if given an argument. Meta-f with a
negative argument moves backward, and Meta-b with a negative argument
moves forward. Forward motion stops right after the last letter of the
word, while backward motion stops right before the first letter.
Meta-d (kill-word) kills the word after point. To be
precise, it kills everything from point to the place Meta-f would
move to. Thus, if point is in the middle of a word, Meta-d kills
just the part after point. If some punctuation comes between point and the
next word, it is killed along with the word. (If you wish to kill only the
next word but not the punctuation before it, simply do Meta-f to get
the end, and kill the word backwards with Meta-DEL.)
Meta-d takes arguments just like Meta-f.
Meta-DEL (backward-kill-word) kills the word before
point. It kills everything from point back to where Meta-b would
move to. If point is after the space in `FOO, BAR', then
`FOO, ' is killed. (If you wish to kill just `FOO', do
Meta-b Meta-d instead of Meta-DEL.)
Meta-t (transpose-words) exchanges the word before or
containing point with the following word. The delimiter characters between
the words do not move. For example, `FOO, BAR' transposes into
`BAR, FOO' rather than `BAR FOO,'. See section Transposing Text, for
more on transposition and on arguments to transposition commands.
To operate on the next n words with an operation which applies
between point and mark, you can either set the mark at point and then move
over the words, or you can use the command Meta-@ (mark-word)
which does not move point, but sets the mark where Meta-f would move
to. It can be given arguments just like Meta-f.
The word commands' understanding of syntax is completely controlled by the syntax table. Any character can, for example, be declared to be a word delimiter. See section The Syntax Table.
The Emacs commands for manipulating sentences and paragraphs are mostly on Meta- keys, so as to be like the word-handling commands.
backward-sentence).
forward-sentence).
kill-sentence).
backward-kill-sentence).
The commands Meta-a and Meta-e (backward-sentence and
forward-sentence) move to the beginning and end of the current
sentence, respectively. They were chosen to resemble Control-a and
Control-e, which move to the beginning and end of a line. Unlike
them, Meta-a and Meta-e if repeated or given numeric arguments
move over successive sentences. Emacs assumes that the typist's convention
is followed, and thus considers a sentence to end wherever there is a
`.', `?' or `!' followed by the end of a line or two spaces,
with any number of `)', `]', `'', or `"' characters
allowed in between. A sentence also begins or ends wherever a paragraph
begins or ends.
Neither M-a nor M-e moves past the newline or spaces beyond the sentence edge at which it is stopping.
Just as C-a and C-e have a kill command, C-k, to go
with them, so M-a and M-e have a corresponding kill command
M-k (kill-sentence) which kills from point to the end of the
sentence. With minus one as an argument it kills back to the beginning of
the sentence. Larger arguments serve as a repeat count.
There is a special command, C-x DEL
(backward-kill-sentence) for killing back to the beginning of a
sentence, because this is useful when you change your mind in the middle of
composing text.
The variable sentence-end controls recognition of the end of a
sentence. It is a regexp that matches the last few characters of a
sentence, together with the whitespace following the sentence. Its
normal value is
"[.?!][]\"')]*\\($\\|\t\\| \\)[ \t\n]*"
This example is explained in the section on regexps. See section Syntax of Regular Expressions.
The Emacs commands for manipulating paragraphs are also Meta- keys.
backward-paragraph).
forward-paragraph).
mark-paragraph).
Meta-[ moves to the beginning of the current or previous paragraph, while Meta-] moves to the end of the current or next paragraph. Blank lines and text formatter command lines separate paragraphs and are not part of any paragraph. Also, an indented line starts a new paragraph.
In major modes for programs (as opposed to Text mode), paragraphs begin and end only at blank lines. This makes the paragraph commands continue to be useful even though there are no paragraphs per se.
When there is a fill prefix, then paragraphs are delimited by all lines which don't start with the fill prefix. See section Filling Text.
When you wish to operate on a paragraph, you can use the command
Meta-h (mark-paragraph) to set the region around it. This
command puts point at the beginning and mark at the end of the paragraph
point was in. If point is between paragraphs (in a run of blank lines, or
at a boundary), the paragraph following point is surrounded by point and
mark. If there are blank lines preceding the first line of the paragraph,
one of these blank lines is included in the region. Thus, for example,
M-h C-w kills the paragraph around or after point.
The precise definition of a paragraph boundary is controlled by the
variables paragraph-separate and paragraph-start. The value
of paragraph-start is a regexp that should match any line that
either starts or separates paragraphs. The value of
paragraph-separate is another regexp that should match only lines
that separate paragraphs without being part of any paragraph. Lines that
start a new paragraph and are contained in it must match both regexps. For
example, normally paragraph-start is "^[ \t\n\f]"
and paragraph-separate is "^[ \t\f]*$".
Normally it is desirable for page boundaries to separate paragraphs. The default values of these variables recognize the usual separator for pages.
Files are often thought of as divided into pages by the formfeed character (ASCII Control-L, octal code 014). For example, if a file is printed on a line printer, each page of the file, in this sense, will start on a new page of paper. Emacs treats a page-separator character just like any other character. It can be inserted with C-q C-l, or deleted with DEL. Thus, you are free to paginate your file or not. However, since pages are often meaningful divisions of the file, commands are provided to move over them and operate on them.
backward-page).
forward-page).
mark-page).
count-lines-page).
The C-x [ (backward-page) command moves point to immediately
after the previous page delimiter. If point is already right after a page
delimiter, it skips that one and stops at the previous one. A numeric
argument serves as a repeat count. The C-x ] (forward-page)
command moves forward past the next page delimiter.
The C-x C-p command (mark-page) puts point at the beginning
of the current page and the mark at the end. The page delimiter at the end
is included (the mark follows it). The page delimiter at the front is
excluded (point follows it). This command can be followed by C-w to
kill a page which is to be moved elsewhere. If it is inserted after a page
delimiter, at a place where C-x ] or C-x [ would take you, then
the page will be properly delimited before and after once again.
A numeric argument to C-x C-p is used to specify which page to go to, relative to the current one. Zero means the current page. One means the next page, and -1 means the previous one.
The C-x l command (count-lines-page) is good for deciding
where to break a page in two. It prints in the echo area the total number
of lines in the current page, and then divides it up into those preceding
the current line and those following, as in
Page has 96 (72+25) lines
Notice that the sum is off by one; this is correct if point is not at the beginning of a line.
The variable page-delimiter should have as its value a regexp that
matches the beginning of a line that separates pages. This is what defines
where pages begin. The normal value of this variable is "^\f",
which matches a formfeed character at the beginning of a line.
With Auto Fill mode, text can be filled (broken up into lines that fit in a specified width) as you insert it. If you alter existing text it may no longer be properly filled; then explicit commands for filling can be used.
Auto Fill mode is a minor mode in which lines are broken automatically when they become too wide. Breaking happens only when you type a SPC or RET.
M-x auto-fill-mode turns Auto Fill mode on if it was off, or off if it was on. With a positive numeric argument it always turns Auto Fill mode on, and with a negative argument always turns it off. You can see when Auto Fill mode is in effect by the presence of the word `Fill' in the mode line, inside the parentheses. Auto Fill mode is a minor mode, turned on or off for each buffer individually. See section Minor Modes.
In Auto Fill mode, lines are broken automatically at spaces when they get longer than the desired width. Line breaking and rearrangement takes place only when you type SPC or RET. If you wish to insert a space or newline without permitting line-breaking, type C-q SPC or C-q LFD (recall that a newline is really a linefeed). Also, C-o inserts a newline without line breaking.
Auto Fill mode works well with Lisp mode, because when it makes a new
line in Lisp mode it indents that line with TAB. If a line ending in
a comment gets too long, the text of the comment is split into two
comment lines. Optionally new comment delimiters are inserted at the end of
the first line and the beginning of the second so that each line is
a separate comment; the variable comment-multi-line controls the
choice (see section Manipulating Comments).
Auto Fill mode does not refill entire paragraphs. It can break lines but cannot merge lines. So editing in the middle of a paragraph can result in a paragraph that is not correctly filled. The easiest way to make the paragraph properly filled again is usually with the explicit fill commands.
Many users like Auto Fill mode and want to use it in all text files. The section on init files says how to arrange this permanently for yourself. See section The Init File, .emacs.
fill-paragraph).
fill-region).
set-fill-column).
To refill a paragraph, use the command Meta-q
(fill-paragraph). It causes the paragraph that point is inside, or
the one after point if point is between paragraphs, to be refilled. All
the line-breaks are removed, and then new ones are inserted where
necessary. M-q can be undone with C-_. See section Undoing Changes.
To refill many paragraphs, use M-g (fill-region), which
divides the region into paragraphs and fills each of them.
Meta-q and Meta-g use the same criteria as Meta-h for finding paragraph boundaries (see section Paragraphs). For more control, you can use M-x fill-region-as-paragraph, which refills everything between point and mark. This command recognizes only blank lines as paragraph separators.
A numeric argument to M-g or M-q causes it to justify the text as well as filling it. This means that extra spaces are inserted to make the right margin line up exactly at the fill column. To remove the extra spaces, use M-q or M-g with no argument.
The command Meta-s (center-line) centers the current line
within the current fill column. With an argument, it centers several lines
individually and moves past them.
The maximum line width for filling is in the variable fill-column.
Altering the value of fill-column makes it local to the current
buffer; until that time, the default value is in effect. The default is
initially 70. See section Local Variables.
The easiest way to set fill-column is to use the command C-x
f (set-fill-column). With no argument, it sets fill-column
to the current horizontal position of point. With a numeric argument, it
uses that as the new fill column.
To fill a paragraph in which each line starts with a special marker (which might be a few spaces, giving an indented paragraph), use the fill prefix feature. The fill prefix is a string which Emacs expects every line to start with, and which is not included in filling.
set-fill-prefix).
fill-paragraph).
To specify a fill prefix, move to a line that starts with the desired
prefix, put point at the end of the prefix, and give the command
C-x . (set-fill-prefix). That's a period after the
C-x. To turn off the fill prefix, specify an empty prefix: type
C-x . with point at the beginning of a line.
When a fill prefix is in effect, the fill commands remove the fill prefix from each line before filling and insert it on each line after filling. The fill prefix is also inserted on new lines made automatically by Auto Fill mode. Lines that do not start with the fill prefix are considered to start paragraphs, both in M-q and the paragraph commands; this is just right if you are using paragraphs with hanging indentation (every line indented except the first one). Lines which are blank or indented once the prefix is removed also separate or start paragraphs; this is what you want if you are writing multi-paragraph comments with a comment delimiter on each line.
The fill prefix is stored in the variable fill-prefix. Its value
is a string, or nil when there is no fill prefix. This is a
per-buffer variable; altering the variable affects only the current buffer,
but there is a default value which you can change as well. See section Local Variables.
Another way to use fill prefixes is through M-x fill-individual-paragraphs. This function divides the region into groups of consecutive lines with the same amount and kind of indentation and fills each group as a paragraph using its indentation as a fill prefix.
Emacs has commands for converting either a single word or any arbitrary range of text to upper case or to lower case.
downcase-word).
upcase-word).
capitalize-word).
downcase-region).
upcase-region).
The word conversion commands are the most useful. Meta-l
(downcase-word) converts the word after point to lower case, moving
past it. Thus, repeating Meta-l converts successive words.
Meta-u (upcase-word) converts to all capitals instead, while
Meta-c (capitalize-word) puts the first letter of the word
into upper case and the rest into lower case. All these commands convert
several words at once if given an argument. They are especially convenient
for converting a large amount of text from all upper case to mixed case,
because you can move through the text using M-l, M-u or
M-c on each word as appropriate, occasionally using M-f instead
to skip a word.
When given a negative argument, the word case conversion commands apply to the appropriate number of words before point, but do not move point. This is convenient when you have just typed a word in the wrong case: you can give the case conversion command and continue typing.
If a word case conversion command is given in the middle of a word, it
applies only to the part of the word which follows point. This is just
like what Meta-d (kill-word) does. With a negative argument,
case conversion applies only to the part of the word before point.
The other case conversion commands are C-x C-u
(upcase-region) and C-x C-l (downcase-region), which
convert everything between point and mark to the specified case. Point and
mark do not move.
Emacs has many commands designed to understand the syntax of programming languages such as Lisp and C. These commands can
The commands for words, sentences and paragraphs are very useful in editing code even though their canonical application is for editing human language text. Most symbols contain words (see section Words); sentences can be found in strings and comments (see section Sentences). Paragraphs per se are not present in code, but the paragraph commands are useful anyway, because Lisp mode and C mode define paragraphs to begin and end at blank lines (see section Paragraphs). Judicious use of blank lines to make the program clearer will also provide interesting chunks of text for the paragraph commands to work on.
The selective display feature is useful for looking at the overall structure of a function (see section Selective Display). This feature causes only the lines that are indented less than a specified amount to appear on the screen.
Emacs also has major modes for the programming languages Lisp, Scheme (a variant of Lisp), C, Fortran and Muddle. Ideally, a major mode should be implemented for each programming language that you might want to edit with Emacs; but often the mode for one language can serve for other syntactically similar languages. The language modes that exist are those that someone decided to take the trouble to write.
There are several forms of Lisp mode, which differ in the way they interface to Lisp execution. See section Major Modes for Lisp.
Each of the programming language modes defines the TAB key to run
an indentation function that knows the indentation conventions of that
language and updates the current line's indentation accordingly. For
example, in C mode TAB is bound to c-indent-line. LFD
is normally defined to do RET followed by TAB; thus, it too
indents in a mode-specific fashion.
In most programming languages, indentation is likely to vary from line to
line. So the major modes for those languages rebind DEL to treat a
tab as if it were the equivalent number of spaces (using the command
backward-delete-char-untabify). This makes it possible to rub out
indentation one column at a time without worrying whether it is made up of
spaces or tabs. Use C-b C-d to delete a tab character before point,
in these modes.
Programming language modes define paragraphs to be separated only by blank lines, so that the paragraph commands remain useful. Auto Fill mode, if enabled in a programming language major mode, indents the new lines which it creates.
Turning on a major mode calls a user-supplied function called the
mode hook, which is the value of a Lisp variable. For example,
turning on C mode calls the value of the variable c-mode-hook if
that value exists and is non-nil. Mode hook variables for other
programming language modes include lisp-mode-hook,
emacs-lisp-mode-hook, lisp-interaction-mode-hook,
scheme-mode-hook and muddle-mode-hook. The mode hook
function receives no arguments.
By convention, Emacs keys for dealing with balanced expressions are usually Control-Meta- characters. They tend to be analogous in function to their Control- and Meta- equivalents. These commands are usually thought of as pertaining to expressions in programming languages, but can be useful with any language in which some sort of parentheses exist (including English).
These commands fall into two classes. Some deal only with lists (parenthetical groupings). They see nothing except parentheses, brackets, braces (whichever ones must balance in the language you are working with), and escape characters that might be used to quote those.
The other commands deal with expressions or sexps. The word `sexp' is derived from s-expression, the ancient term for an expression in Lisp. But in Emacs, the notion of `sexp' is not limited to Lisp. It refers to an expression in whatever language your program is written in. Each programming language has its own major mode, which customizes the syntax tables so that expressions in that language count as sexps.
Sexps typically include symbols, numbers, and string constants, as well as anything contained in parentheses, brackets or braces.
In languages that use prefix and infix operators, such as C, it is not possible for all expressions to be sexps. For example, C mode does not recognize `foo + bar' as a sexp, even though it is a C expression; it recognizes `foo' as one sexp and `bar' as another, with the `+' as punctuation between them. This is a fundamental ambiguity: both `foo + bar' and `foo' are legitimate choices for the sexp to move over if point is at the `f'. Note that `(foo + bar)' is a sexp in C mode.
Some languages have obscure forms of syntax for expressions that nobody has bothered to make Emacs understand properly.
forward-sexp).
backward-sexp).
kill-sexp).
backward-up-list).
down-list).
forward-list).
backward-list).
transpose-sexps).
mark-sexp).
To move forward over a sexp, use C-M-f (forward-sexp). If
the first significant character after point is an opening delimiter
(`(' in Lisp; `(', `[' or `{' in C), C-M-f
moves past the matching closing delimiter. If the character begins a
symbol, string, or number, C-M-f moves over that. If the character
after point is a closing delimiter, C-M-f just moves past it. (This
last is not really moving across a sexp; it is an exception which is
included in the definition of C-M-f because it is as useful a
behavior as anyone can think of for that situation.)
The command C-M-b (backward-sexp) moves backward over a
sexp. The detailed rules are like those above for C-M-f, but with
directions reversed. If there are any prefix characters (singlequote,
backquote and comma, in Lisp) preceding the sexp, C-M-b moves back
over them as well.
C-M-f or C-M-b with an argument repeats that operation the specified number of times; with a negative argument, it moves in the opposite direction.
The sexp commands move across comments as if they were whitespace, in languages such as C where the comment-terminator can be recognized. In Lisp, and other languages where comments run until the end of a line, it is very difficult to ignore comments when parsing backwards; therefore, in such languages the sexp commands treat the text of comments as if it were code.
Killing a sexp at a time can be done with C-M-k (kill-sexp).
C-M-k kills the characters that C-M-f would move over.
The list commands move over lists like the sexp commands but skip
blithely over any number of other kinds of sexps (symbols, strings, etc).
They are C-M-n (forward-list) and C-M-p
(backward-list). The main reason they are useful is that they
usually ignore comments (since the comments usually do not contain any
lists).
C-M-n and C-M-p stay at the same level in parentheses, when
that's possible. To move up one (or n) levels, use C-M-u
(backward-up-list).
C-M-u moves backward up past one unmatched opening delimiter. A
positive argument serves as a repeat count; a negative argument reverses
direction of motion and also requests repetition, so it moves forward and
up one or more levels.
To move down in list structure, use C-M-d (down-list). In Lisp mode,
where `(' is the only opening delimiter, this is nearly the same as
searching for a `('. An argument specifies the number of levels
of parentheses to go down.
A somewhat random-sounding command which is nevertheless easy to use is
C-M-t (transpose-sexps), which drags the previous sexp across
the next one. An argument serves as a repeat count, and a negative
argument drags backwards (thus canceling out the effect of C-M-t with
a positive argument). An argument of zero, rather than doing nothing,
transposes the sexps ending after point and the mark.
To make the region be the next sexp in the buffer, use C-M-@
(mark-sexp) which sets mark at the same place that C-M-f would
move to. C-M-@ takes arguments like C-M-f. In particular, a
negative argument is useful for putting the mark at the beginning of the
previous sexp.
The list and sexp commands' understanding of syntax is completely controlled by the syntax table. Any character can, for example, be declared to be an opening delimiter and act like an open parenthesis. See section The Syntax Table.
In Emacs, a parenthetical grouping at the top level in the buffer is
called a defun. The name derives from the fact that most top-level
lists in a Lisp file are instances of the special form defun, but
any top-level parenthetical grouping counts as a defun in Emacs parlance
regardless of what its contents are, and regardless of the programming
language in use. For example, in C, the body of a function definition is a
defun.
beginning-of-defun).
end-of-defun).
mark-defun).
The commands to move to the beginning and end of the current defun are
C-M-a (beginning-of-defun) and C-M-e (end-of-defun).
If you wish to operate on the current defun, use C-M-h
(mark-defun) which puts point at the beginning and mark at the end
of the current or next defun. For example, this is the easiest way to get
ready to move the defun to a different place in the text. In C mode,
C-M-h runs the function mark-c-function, which is almost the
same as mark-defun; the difference is that it backs up over the
argument declarations, function name and returned data type so that the
entire C function is inside the region.
Emacs assumes that any open-parenthesis found in the leftmost column is the start of a defun. Therefore, never put an open-parenthesis at the left margin in a Lisp file unless it is the start of a top level list. Never put an open-brace or other opening delimiter at the beginning of a line of C code unless it starts the body of a function. The most likely problem case is when you want an opening delimiter at the start of a line inside a string. To avoid trouble, put an escape character (`\', in C and Emacs Lisp, `/' in some other Lisp dialects) before the opening delimiter. It will not affect the contents of the string.
In the remotest past, the original Emacs found defuns by moving upward a level of parentheses until there were no more levels to go up. This always required scanning all the way back to the beginning of the buffer, even for a small function. To speed up the operation, Emacs was changed to assume that any `(' (or other character assigned the syntactic class of opening-delimiter) at the left margin is the start of a defun. This heuristic was nearly always right and avoided the costly scan; however, it mandated the convention described above.
The best way to keep a program properly indented ("ground") is to use Emacs to re-indent it as you change it. Emacs has commands to indent properly either a single line, a specified number of lines, or all of the lines inside a single parenthetical grouping.
newline-and-indent).
The basic indentation command is TAB, which gives the current line
the correct indentation as determined from the previous lines. The
function that TAB runs depends on the major mode; it is lisp-indent-line
in Lisp mode, c-indent-line in C mode, etc. These functions
understand different syntaxes for different languages, but they all do
about the same thing. TAB in any programming language major mode
inserts or deletes whitespace at the beginning of the current line,
independent of where point is in the line. If point is inside the
whitespace at the beginning of the line, TAB leaves it at the end of
that whitespace; otherwise, TAB leaves point fixed with respect to
the characters around it.
Use C-q TAB to insert a tab at point.
When entering a large amount of new code, use LFD (newline-and-indent),
which is equivalent to a RET followed by a TAB. LFD creates
a blank line, and then gives it the appropriate indentation.
TAB indents the second and following lines of the body of an parenthetical grouping each under the preceding one; therefore, if you alter one line's indentation to be nonstandard, the lines below will tend to follow it. This is the right behavior in cases where the standard result of TAB is unaesthetic.
Remember that an open-parenthesis, open-brace or other opening delimiter at the left margin is assumed by Emacs (including the indentation routines) to be the start of a function. Therefore, you must never have an opening delimiter in column zero that is not the beginning of a function, not even inside a string. This restriction is vital for making the indentation commands fast; you must simply accept it. See section Defuns, for more information on this.
When you wish to re-indent several lines of code which have been altered or moved to a different level in the list structure, you have several commands available.
indent-sexp).
indent-region).
You can re-indent the contents of a single list by positioning point
before the beginning of it and typing C-M-q (indent-sexp in
Lisp mode, indent-c-exp in C mode; also bound to other suitable
functions in other modes). The indentation of the line the sexp starts on
is not changed; therefore, only the relative indentation within the list,
and not its position, is changed. To correct the position as well, type a
TAB before the C-M-q.
If the relative indentation within a list is correct but the indentation of its beginning is not, go to the line the list begins on and type C-u TAB. When TAB is given a numeric argument, it moves all the lines in the grouping starting on the current line sideways the same amount that the current line moves. It is clever, though, and does not move lines that start inside strings, or C preprocessor lines when in C mode.
Another way to specify the range to be re-indented is with point and
mark. The command C-M-\ (indent-region) applies TAB to every line
whose first character is between point and mark.
The indentation pattern for a Lisp expression can depend on the function called by the expression. For each Lisp function, you can choose among several predefined patterns of indentation, or define an arbitrary one with a Lisp program.
The standard pattern of indentation is as follows: the second line of the expression is indented under the first argument, if that is on the same line as the beginning of the expression; otherwise, the second line is indented underneath the function name. Each following line is indented under the previous line whose nesting depth is the same.
If the variable lisp-indent-offset is non-nil, it overrides
the usual indentation pattern for the second line of an expression, so that
such lines are always indented lisp-indent-offset more columns than
the containing list.
The standard pattern is overridded for certain functions. Functions
whose names start with def always indent the second line by
lisp-body-indention extra columns beyond the open-parenthesis
starting the expression.
The standard pattern can be overridden in various ways for individual
functions, according to the lisp-indent-hook property of the
function name. There are four possibilities for this property:
nil
defun
def is used for
this function also.
lisp-body-indent
more columns than the open-parenthesis starting the containing
expression. If the argument is distinguished and is either the first
or second argument, it is indented twice that many extra columns.
If the argument is distinguished and not the first or second argument,
the standard pattern is followed for that line.
parse-partial-sexp (a Lisp primitive for
indentation and nesting computation) when it parses up to the
beginning of this line.
Two variables control which commands perform C indentation and when.
If c-auto-newline is non-nil, newlines are inserted both
before and after braces that you insert, and after colons and semicolons.
Correct C indentation is done on all the lines that are made this way.
If c-tab-always-indent is non-nil, the TAB command
in C mode does indentation only if point is at the left margin or within
the line's indentation. If there is non-whitespace to the left of point,
then TAB just inserts a tab character in the buffer. Normally,
this variable is nil, and TAB always reindents the current line.
C does not have anything analogous to particular function names for which special forms of indentation are desirable. However, it has a different need for customization facilities: many different styles of C indentation are in common use.
There are six variables you can set to control the style that Emacs C mode will use.
c-indent-level
c-continued-statement-offset
c-brace-offset
c-brace-imaginary-offset
c-argdecl-indent
c-label-offset
The variable c-indent-level controls the indentation for C
statements with respect to the surrounding block. In the example
{
foo ();
the difference in indentation between the lines is c-indent-level.
Its standard value is 2.
If the open-brace beginning the compound statement is not at the beginning
of its line, the c-indent-level is added to the indentation of the
line, not the column of the open-brace. For example,
if (losing) {
do_this ();
One popular indentation style is that which results from setting
c-indent-level to 8 and putting open-braces at the end of a line in
this way. I prefer to put the open-brace on a separate line.
In fact, the value of the variable c-brace-imaginary-offset is
also added to the indentation of such a statement. Normally this variable
is zero. Think of this variable as the imaginary position of the open
brace, relative to the first nonblank character on the line. By setting
this variable to 4 and c-indent-level to 0, you can get this style:
if (x == y) {
do_it ();
}
When c-indent-level is zero, the statements inside most braces
will line up right under the open brace. But there is an exception made
for braces in column zero, such as surrounding a function's body. The
statements just inside it do not go at column zero. Instead,
c-brace-offset and c-continued-statement-offset (see below)
are added to produce a typical offset between brace levels, and the
statements are indented that far.
c-continued-statement-offset controls the extra indentation for a
line that starts within a statement (but not within parentheses or
brackets). These lines are usually statements that are within other
statements, such as the then-clauses of if statements and the bodies
of while statements. This parameter is the difference in
indentation between the two lines in
if (x == y) do_it ();
Its standard value is 2. Some popular indentation styles correspond to a
value of zero for c-continued-statement-offset.
c-brace-offset is the extra indentation given to a line that
starts with an open-brace. Its standard value is zero;
compare
if (x == y)
{
with
if (x == y) do_it ();
if c-brace-offset were set to 4, the first example would become
if (x == y)
{
c-argdecl-indent controls the indentation of declarations of the
arguments of a C function. It is absolute: argument declarations receive
exactly c-argdecl-indent spaces. The standard value is 5, resulting
in code like this:
char *
index (string, char)
char *string;
int char;
c-label-offset is the extra indentation given to a line that
contains a label, a case statement, or a default: statement. Its
standard value is -2, resulting in code like this
switch (c)
{
case 'x':
If c-label-offset were zero, the same code would be indented as
switch (c)
{
case 'x':
This example assumes that the other variables above also have their standard values.
I strongly recommend that you try out the indentation style produced by the standard settings of these variables, together with putting open braces on separate lines. You can see how it looks in all the C source files of GNU Emacs.
The Emacs parenthesis-matching feature is designed to show automatically how parentheses match in the text. Whenever a self-inserting character that is a closing delimiter is typed, the cursor moves momentarily to the location of the matching opening delimiter, provided that is on the screen. If it is not on the screen, some text starting with that opening delimiter is displayed in the echo area. Either way, you can tell what grouping is being closed off.
In Lisp, automatic matching applies only to parentheses. In C, it applies to braces and brackets too. Emacs knows which characters to regard as matching delimiters based on the syntax table, which is set by the major mode. See section The Syntax Table.
If the opening delimiter and closing delimiter are mismatched--such as in `[x)'---a warning message is displayed in the echo area. The correct matches are specified in the syntax table.
Two variables control parenthesis match display. blink-matching-paren
turns the feature on or off; nil turns it off, but the default is
t to turn match display on. blink-matching-paren-distance
specifies how many characters back to search to find the matching opening
delimiter. If the match is not found in that far, scanning stops, and
nothing is displayed. This is to prevent scanning for the matching
delimiter from wasting lots of time when there is no match. The default
is 4000.
The comment commands insert, kill and align comments.
indent-for-comment).
set-comment-column).
kill-comment).
indent-new-comment-line).
The command that creates a comment is Meta-; (indent-for-comment).
If there is no comment already on the line, a new comment is created,
aligned at a specific column called the comment column. The comment
is created by inserting the string Emacs thinks comments should start with
(the value of comment-start; see below). Point is left after that
string. If the text of the line extends past the comment column, then the
indentation is done to a suitable boundary (usually, at least one space is
inserted). If the major mode has specified a string to terminate comments,
that is inserted after point, to keep the syntax valid.
Meta-; can also be used to align an existing comment. If a line already contains the string that starts comments, then M-; just moves point after it and re-indents it to the conventional place. Exception: comments starting in column 0 are not moved.
Some major modes have special rules for indenting certain kinds of comments in certain contexts. For example, in Lisp code, comments which start with two semicolons are indented as if they were lines of code, instead of at the comment column. Comments which start with three semicolons are supposed to start at the left margin. Emacs understands these conventions by indenting a double-semicolon comment using TAB, and by not changing the indentation of a triple-semicolon comment at all.
;; This function is just an example ;;; Here either two or three semicolons are appropriate. (defun foo (x) ;;; And now, the first part of the function: ;; The following line adds one. (1+ x)) ; This line adds one.
In C code, a comment preceded on its line by nothing but whitespace is indented like a line of code.
Even when an existing comment is properly aligned, M-; is still useful for moving directly to the start of the comment.
C-u - C-x ; (kill-comment) kills the comment on the current line,
if there is one. The indentation before the start of the comment is killed
as well. If there does not appear to be a comment in the line, nothing is
done. To reinsert the comment on another line, move to the end of that
line, do C-y, and then do M-; to realign it. Note that
C-u - C-x ; is not a distinct key; it is C-x ; (set-comment-column)
with a negative argument. That command is programmed so that when it
receives a negative argument it calls kill-comment. However,
kill-comment is a valid command which you could bind directly to a
key if you wanted to.
If you are typing a comment and find that you wish to continue it on
another line, you can use the command Meta-LFD (indent-new-comment-line),
which terminates the comment you are typing, creates a new blank line
afterward, and begins a new comment indented under the old one. When Auto
Fill mode is on, going past the fill column while typing a comment causes
the comment to be continued in just this fashion. If point is not at the
end of the line when M-LFD is typed, the text on the rest of
the line becomes part of the new comment line.
The comment column is stored in the variable comment-column. You
can set it to a number explicitly. Alternatively, the command C-x ;
(set-comment-column) sets the comment column to the column point is
at. C-u C-x ; sets the comment column to match the last comment
before point in the buffer, and then does a Meta-; to align the
current line's comment under the previous one. Note that C-u - C-x ;
runs the function kill-comment as described above.
comment-column is a per-buffer variable; altering the variable
affects only the current buffer, but there is a default value which you can
change as well. See section Local Variables. Many major modes initialize this variable
for the current buffer.
The comment commands recognize comments based on the regular expression
that is the value of the variable comment-start-skip. This regexp
should not match the null string. It may match more than the comment
starting delimiter in the strictest sense of the word; for example, in C
mode the value of the variable is "/\\*+ *", which matches extra
stars and spaces after the `/*' itself. (Note that `\\' is
needed in Lisp syntax to include a `\' in the string, which is needed
to deny the first star its special meaning in regexp syntax. See section Syntax of Regular Expressions.)
When a comment command makes a new comment, it inserts the value of
comment-start to begin it. The value of comment-end is
inserted after point, so that it will follow the text that you will insert
into the comment. In C mode, comment-start has the value
"/* " and comment-end has the value " */".
comment-multi-line controls how M-LFD (indent-new-comment-line)
behaves when used inside a comment. If comment-multi-line is
nil, as it normally is, then the comment on the starting line is
terminated and a new comment is started on the new following line. If
comment-multi-line is not nil, then the new following line is
set up as part of the same comment that was found on the starting line.
This is done by not inserting a terminator on the old line, and not
inserting a starter on the new line. In languages where multi-line comments
work, the choice of value for this variable is a matter of taste.
The variable comment-indent-hook should contain a function that
will be called to compute the indentation for a newly inserted comment or
for aligning an existing comment. It is set differently by various major
modes. The function is called with no arguments, but with point at the
beginning of the comment, or at the end of a line if a new comment is to be
inserted. It should return the column in which the comment ought to start.
For example, in Lisp mode, the indent hook function bases its decision
on how many semicolons begin an existing comment, and on the code in the
preceding lines.
insert-parentheses).
move-over-close-and-reindent).
The commands M-( (insert-parentheses) and M-)
(move-over-close-and-reindent) are designed to facilitate a style of
editing which keeps parentheses balanced at all times. M-( inserts a
pair of parentheses, either together as in `()', or, if given an
argument, around the next several sexps, and leaves point after the open
parenthesis. Instead of typing ( F O O ), you can type M-( F O
O, which has the same effect except for leaving the cursor before the
close parenthesis. Then you would type M-), which moves past the
close parenthesis, deleting any indentation preceding it (in this example
there is none), and indenting with LFD after it.
Usually completion happens in the minibuffer. But one kind of completion is available in all buffers: completion for Lisp symbol names.
The command M-TAB (lisp-complete-symbol) takes the
partial Lisp symbol before point to be an abbreviation, and compares it
against all nontrivial Lisp symbols currently known to Emacs. Any
additional characters that they all have in common are inserted at point.
Nontrivial symbols are those that have function definitions, values or
properties.
If there is an open-parenthesis immediately before the beginning of the partial symbol, only symbols with function definitions are considered as completions.
If the partial name in the buffer has more than one possible completion and they have no additional characters in common, a list of all possible completions is displayed in another window.
As you edit Lisp code to be run in Emacs, the commands C-h f
(describe-function) and C-h v (describe-variable) can
be used to print documentation of functions and variables that you want to
call. These commands use the minibuffer to read the name of a function or
variable to document, and display the documentation in a window.
For extra convenience, these commands provide default arguments based on the code in the neighborhood of point. C-h f sets the default to the function called in the innermost list containing point. C-h v uses the symbol name around or adjacent to point as its default.
Documentation on Unix commands, system calls and libraries can be
obtained with the M-x manual-entry command. This reads a topic as an
argument, and displays the text on that topic from the Unix manual.
manual-entry always searches all 8 sections of the manual, and
concatenates all the entries that are found. For example, the topic
`termcap' finds the description of the termcap library from section 3,
followed by the description of the termcap data base from section 5.
The Emacs command M-x add-change-log-entry helps you keep a record of when and why you have changed a program. It assumes that you have a file in which you write a chronological sequence of entries describing individual changes. The default is to store the change entries in a file called `ChangeLog' in the same directory as the file you are editing. The same `ChangeLog' file therefore records changes for all the files in the directory.
A change log entry starts with a header line that contains your name and the current date. Aside from these header lines, every line in the change log starts with a tab. One entry can describe several changes; each change starts with a line starting with a tab and a star. M-x add-change-log-entry visits the change log file and creates a new entry unless the most recent entry is for today's date and your name. In either case, it adds a new line to start the description of another change just after the header line of the entry. When M-x add-change-log-entry is finished, all is prepared for you to edit in the description of what you changed and how. You must then save the change log file yourself.
The change log file is always visited in Indented Text mode, which means that LFD and auto-filling indent each new line like the previous line. This is convenient for entering the contents of an entry, which must all be indented. See section Text Mode.
Here is an example of the formatting conventions used in the change log for Emacs:
Wed Jun 26 19:29:32 1985 Richard M. Stallman (rms at mit-prep)
* xdisp.c (try_window_id):
If C-k is done at end of next-to-last line,
this fn updates window_end_vpos and cannot leave
window_end_pos nonnegative (it is zero, in fact).
If display is preempted before lines are output,
this is inconsistent. Fix by setting
blank_end_of_window to nonzero.
Tue Jun 25 05:25:33 1985 Richard M. Stallman (rms at mit-prep)
* cmds.c (Fnewline):
Call the auto fill hook if appropriate.
* xdisp.c (try_window_id):
If point is found by compute_motion after xp, record that
permanently. If display_text_line sets point position wrong
(case where line is killed, point is at eob and that line is
not displayed), set it again in final compute_motion.
A tag table is a description of how a multi-file program is broken up into files. It lists the names of the component files and the names and positions of the functions in each file. Grouping the related files makes it possible to search or replace through all the files with one command. Recording the function names and positions makes possible the Meta-. command which you can use to find the definition of a function without having to know which of the files it is in.
Tag tables are stored in files called tag table files. The conventional name for a tag table file is `TAGS'.
Each entry in the tag table records the name of one tag, the name of the file that the tag is defined in (implicitly), and the position in that file of the tag's definition.
Just what names from the described files are recorded in the tag table depends on the programming language of the described file. They normally include all functions and subroutines, and may also include global variables, data types, and anything else convenient. In any case, each name recorded is called a tag.
In Lisp code, any function defined with defun, any variable
defined with defvar or defconst, and in general the first
argument of any expression that starts with `(def' in column zero, is
a tag.
In C code, any C function is a tag, and so is any typedef if -t is
specified when the tag table is constructed.
In Fortran code, functions and subroutines are tags.
In LaTeX text, the argument of any of the commands \chapter,
\section, \subsection, \subsubsection, \eqno,
\label, \ref, \cite, \bibitem and
\typeout is a tag.
The etags program is used to create a tag table file. It knows
the syntax of C, Fortran, LaTeX, Scheme and Emacs Lisp/Common Lisp. To
use etags, type
etags inputfiles...
as a shell command. It reads the specified files and writes a tag table
named `TAGS' in the current working directory. etags
recognizes the language used in an input file based on its file name and
contents; there are no switches for specifying the language. The -t
switch tells etags to record typedefs in C code as tags.
If the tag table data become outdated due to changes in the files described in the table, the way to update the tag table is the same way it was made in the first place. It is not necessary to do this often.
If the tag table fails to record a tag, or records it for the wrong file, then Emacs cannot possibly find its definition. However, if the position recorded in the tag table becomes a little bit wrong (due to some editing in the file that the tag definition is in), the only consequence is to slow down finding the tag slightly. Even if the stored position is very wrong, Emacs will still find the tag, but it must search the entire file for it.
So you should update a tag table when you define new tags that you want to have listed, or when you move tag definitions from one file to another, or when changes become substantial. Normally there is no need to update the tag table after each edit, or even every day.
Emacs has at any time one selected tag table, and all the commands for working with tag tables use the selected one. To select a tag table, type M-x visit-tags-table, which reads the tag table file name as an argument. The name `TAGS' in the default directory is used as the default file name.
All this command does is store the file name in the variable
tags-file-name. Emacs does not actually read in the tag table
contents until you try to use them. Setting this variable yourself is just
as good as using visit-tags-table. The variable's initial value is
nil; this value tells all the commands for working with tag tables
that they must ask for a tag table file name to use.
The most important thing that a tag table enables you to do is to find the definition of a specific tag.
find-tag).
find-tag-other-window).
M-. (find-tag) is the command to find the definition of a
specified tag. It searches through the tag table for that tag, as a
string, and then uses the tag table info to determine the file that the
definition is in and the approximate character position in the file of the
definition. Then find-tag visits that file, moves point to the
approximate character position, and starts searching ever-increasing
distances away for the the text that should appear at the beginning of the
definition.
If an empty argument is given (just type RET), the sexp in the buffer before or around point is used as the name of the tag to find. See section Lists and Sexps, for info on sexps.
The argument to find-tag need not be the whole tag name; it can be
a substring of a tag name. However, there can be many tag names containing
the substring you specify. Since find-tag works by searching the
text of the tag table, it finds the first tag in the table that the
specified substring appears in. The way to find other tags that match the
substring is to give find-tag a numeric argument, as in C-u
M-.; this does not read a tag name, but continues searching the tag
table's text for another tag containing the same substring last used. If
you have a real META key, M-0 M-. is an easier alternative
to C-u M-..
Like most commands that can switch buffers, find-tag has another
similar command that displays the new buffer in another window. C-x 4
. invokes the function find-tag-other-window. (This key sequence
ends with a period.)
Emacs comes with a tag table file `TAGS', in the directory
containing Lisp libraries, which includes all the Lisp libraries and all
the C sources of Emacs. By specifying this file with visit-tags-table
and then using M-. you can quickly look at the source of any Emacs
function.
The commands in this section visit and search all the files listed in the selected tag table, one by one. For these commands, the tag table serves only to specify a sequence of files to search. A related command is M-x grep (see section Running `make', or Compilers Generally).
query-replace on each file in the selected tag table.
tags-loop-continue).
M-x tags-search reads a regexp using the minibuffer, then visits
the files of the selected tag table one by one, and searches through each
one for that regexp. It displays the name of the file being searched so
you can follow its progress. As soon as an occurrence is found,
tags-search returns.
Having found one match, you probably want to find all the rest. To find
one more match, type M-, (tags-loop-continue) to resume the
tags-search. This searches the rest of the current buffer, followed
by the remaining files of the tag table.
M-x tags-query-replace performs a single query-replace
through all the files in the tag table. It reads a string to search for
and a string to replace with, just like ordinary M-x query-replace.
It searches much like M-x tags-search but repeatedly, processing
matches according to your input. See section Replacement Commands, for more information on
query-replace.
It is possible to get through all the files in the tag table with a single invocation of M-x tags-query-replace. But since any unrecognized character causes the command to exit, you may need to continue where you left off. M-, can be used for this. It resumes the last tags search or replace command that you did.
It may have struck you that tags-search is a lot like grep.
You can also run grep itself as an inferior of Emacs and have Emacs
show you the matching lines one by one. This works mostly the same as
running a compilation and having Emacs show you where the errors were.
See section Running `make', or Compilers Generally.
If you wish to process all the files in the selected tag table, but M-x tags-search and M-x tags-query-replace in particular are not what you want, you can use M-x next-file.
M-x list-tags reads the name of one of the files described by the selected tag table, and displays a list of all the tags defined in that file. The "file name" argument is really just a string to compare against the names recorded in the tag table; it is read as a string rather than as a file name. Therefore, completion and defaulting are not available, and you must enter the string the same way it appears in the tag table. Do not include a directory as part of the file name unless the file name recorded in the tag table includes a directory.
M-x tags-apropos is like apropos for tags. It reads a regexp,
then finds all the tags in the selected tag table whose entries match that
regexp, and displays the tag names found.
Fortran mode provides special motion commands for Fortran statements and subprograms, and indentation commands that understand Fortran conventions of nesting, line numbers and continuation statements.
Special commands for comments are provided because Fortran comments are unlike those of other languages.
Built-in abbrevs optionally save typing when you insert Fortran keywords.
Use M-x fortran-mode to switch to this major mode. Doing so calls
the value of fortran-mode-hook as a function of no arguments if
that variable has a value that is not nil.
Fortran mode was contributed by Michael Prange.
Fortran mode provides special commands to move by subprograms (functions and subroutines) and by statements. There is also a command to put the region around one subprogram, convenient for killing it or moving it.
beginning-of-fortran-subprogram).
end-of-fortran-subprogram).
mark-fortran-subprogram).
fortran-next-statement).
fortran-previous-statement).
Special commands and features are needed for indenting Fortran code in order to make sure various syntactic entities (line numbers, comment line indicators and continuation line flags) appear in the columns that are required for standard Fortran.
fortran-indent-line).
fortran-indent-subprogram).
TAB is redefined by Fortran mode to reindent the current line for
Fortran (fortran-indent-line). Line numbers and continuation
markers are indented to their required columns, and the body of the
statement is independently indented based on its nesting in the program.
The key C-M-q is redefined as fortran-indent-subprogram, a
command to reindent all the lines of the Fortran subprogram (function or
subroutine) containing point.
The key M-LFD is redefined as fortran-split-line, a
command to split a line in the appropriate fashion for Fortran. In a
non-comment line, the second half becomes a continuation line and is
indented accordingly. In a comment line, both halves become separate
comment lines.
If a number is the first non-whitespace in the line, it is assumed to be a line number and is moved to columns 0 through 4. (Columns are always counted from 0 in GNU Emacs.) If the text on the line starts with the conventional Fortran continuation marker `$', it is moved to column 5. If the text begins with any non whitespace character in column 5, it is assumed to be an unconventional continuation marker and remains in column 5.
Line numbers of four digits or less are normally indented one space.
This amount is controlled by the variable fortran-line-number-indent
which is the maximum indentation a line number can have. Line numbers
are indented to right-justify them to end in column 4 unless that would
require more than this maximum indentation. The default value of the
variable is 1.
Simply inserting a line number is enough to indent it according to these
rules. As each digit is inserted, the indentation is recomputed. To turn
off this feature, set the variable fortran-electric-line-number to
nil. Then inserting line numbers is like inserting anything else.
Fortran mode assumes that you follow certain conventions that simplify the task of understanding a Fortran program well enough to indent it properly:
fortran-continuation-char.
By default, this character is `$'.
If you fail to follow these conventions, the indentation commands may indent some lines unaesthetically. However, a correct Fortran program will retain its meaning when reindented even if the conventions are not followed.
Several additional variables control how Fortran indentation works.
fortran-do-indent
fortran-if-indent
fortran-continuation-indent
fortran-check-all-num-for-matching-do
nil, indentation assumes that each `do'
statement ends on a `continue' statement. Therefore, when
computing indentation for a statement other than `continue', it
can save time by not checking for a `do' statement ending there.
If this is non-nil, indenting any numbered statement must check
for a `do' that ends there. The default is nil.
fortran-minimum-statement-indent
The usual Emacs comment commands assume that a comment can follow a line of code. In Fortran, the standard comment syntax requires an entire line to be just a comment. Therefore, Fortran mode replaces the standard Emacs comment commands and defines some new variables.
Fortran mode can also handle a nonstandard comment syntax where comments
start with `!' and can follow other text. Because only some Fortran
compilers accept this syntax, Fortran mode will not insert such comments
unless you have said in advance to do so. To do this, set the variable
comment-start to `"!"' (see section Variables).
fortran-comment-indent).
fortran-comment-region).
M-; in Fortran mode is redefined as the command
fortran-comment-indent. Like the usual M-; command, this
recognizes any kind of existing comment and aligns its text appropriately;
if there is no existing comment, a comment is inserted and aligned. But
inserting and aligning comments are not the same in Fortran mode as in
other modes.
When a new comment must be inserted, if the current line is blank, a full-line comment is inserted. On a non-blank line, a nonstandard `!' comment is inserted if you have said you want to use them. Otherwise a full-line comment is inserted on a new line before the current line.
Nonstandard `!' comments are aligned like comments in other
languages, but full-line comments are different. In a standard full-line
comment, the comment delimiter itself must always appear in column zero.
What can be aligned is the text within the comment. You can choose from
three styles of alignment by setting the variable
fortran-comment-indent-style to one of these values:
fixed
fortran-comment-line-column. This is the default.
relative
fortran-comment-line-column columns of indentation.
nil
In addition, you can specify the character to be used to indent within
full-line comments by setting the variable fortran-comment-indent-char
to the character you want to use.
Fortran mode introduces two variables comment-line-start and
comment-line-start-skip which play for full-line comments the same
roles played by comment-start and comment-start-skip for
ordinary text-following comments. Normally these are set properly by
Fortran mode so you do not need to change them.
The normal Emacs comment command C-x ; has not been redefined. If you use `!' comments, this command can be used with them. Otherwise it is useless in Fortran mode.
The command C-c ; (fortran-comment-region) turns all the
lines of the region into comments by inserting the string `C$$$' at
the front of each one. With a numeric arg, the region is turned back into
live code by deleting `C$$$' from the front of each line in it. The
string used for these comments can be controlled by setting the variable
fortran-comment-region. Note that here we have an example of a
command and a variable with the same name; these two uses of the name never
conflict because in Lisp and in Emacs it is always clear from the context
which one is meant.
fortran-column-ruler).
fortran-window-create).
The command C-c C-r (fortran-column-ruler) shows a column
ruler momentarily above the current line. The comment ruler is two lines
of text that show you the locations of columns with special significance
in Fortran programs. Square brackets show the limits of the columns for
line numbers, and curly brackets show the limits of the columns for the
statement body. Column numbers appear above them.
Note that the column numbers count from zero, as always in GNU Emacs. As a result, the numbers may not be those you are familiar with; but the actual positions in the line are standard Fortran.
The text used to display the column ruler is the value of the variable
fortran-comment-ruler. By changing this variable, you can change
the display.
For even more help, use C-c C-w (fortran-window-create), a
command which splits the current window horizontally, making a window 72
columns wide. By editing in this window you can immediately see when you
make a line too wide to be correct Fortran.
Fortran mode provides many built-in abbrevs for common keywords and declarations. These are the same sort of abbrev that you can define yourself. To use them, you must turn on Abbrev mode. see section Abbrevs.
The built-in abbrevs are unusual in one way: they all start with a semicolon. You cannot normally use semicolon in an abbrev, but Fortran mode makes this possible by changing the syntax of semicolon to "word constituent".
For example, one built-in Fortran abbrev is `;c' for `continue'. If you insert `;c' and then insert a punctuation character such as a space or a newline, the `;c' will change automatically to `continue', provided Abbrev mode is enabled.
Type `;?' or `;C-h' to display a list of all the built-in Fortran abbrevs and what they stand for.
The previous chapter discusses the Emacs commands that are useful for making changes in programs. This chapter deals with commands that assist in the larger process of developing and maintaining programs.
Emacs can run compilers for noninteractive languages such as C and Fortran as inferior processes, feeding the error log into an Emacs buffer. It can also parse the error messages and visit the files in which errors are found, moving point right to the line where the error occurred.
grep asynchronously under Emacs, with matching lines
listed in the buffer named `*compilation*'.
grep subprocess.
grep match.
To run make or another compiler, do M-x compile. This command
reads a shell command line using the minibuffer, and then executes the
specified command line in an inferior shell with output going to the buffer
named `*compilation*'. The current buffer's default directory is used
as the working directory for the execution of the command; normally,
therefore, the makefile comes from this directory.
When the shell command line is read, the minibuffer appears containing a
default command line, which is the command you used the last time you did
M-x compile. If you type just RET, the same command line is used
again. The first M-x compile provides make -k as the default.
The default is taken from the variable compile-command; if the
appropriate compilation command for a file is something other than
make -k, it can be useful to have the file specify a local value for
compile-command (see section Local Variables in Files).
Starting a compilation causes the buffer `*compilation*' to be displayed in another window but not selected. Its mode line tells you whether compilation is finished, with the word `run' or `exit' inside the parentheses. You do not have to keep this buffer visible; compilation continues in any case.
To kill the compilation process, do M-x kill-compilation. You will see that the mode line of the `*compilation*' buffer changes to say `signal' instead of `run'. Starting a new compilation also kills any running compilation, as only one can exist at any time. However, this requires confirmation before actually killing a compilation that is running.
To parse the compiler error messages, type C-x ` (next-error). The
character following the C-x is the grave accent, not the single
quote. This command displays the buffer `*compilation*' in one window
and the buffer in which the next error occurred in another window. Point
in that buffer is moved to the line where the error was found. The
corresponding error message is scrolled to the top of the window in which
`*compilation*' is displayed.
The first time C-x ` is used after the start of a compilation, it parses all the error messages, visits all the files that have error messages, and makes markers pointing at the lines that the error messages refer to. Then it moves to the first error message location. Subsequent uses of C-x ` advance down the data set up by the first use. When the preparsed error messages are exhausted, the next C-x ` checks for any more error messages that have come in; this is useful if you start editing the compiler errors while the compilation is still going on. If no more error messages have come in, C-x ` reports an error.
C-u C-x ` discards the preparsed error message data and parses the `*compilation*' buffer over again, then displaying the first error. This way, you can process the same set of errors again.
Instead of running a compiler, you can run grep and see the lines
on which matches were found. To do this, type M-x grep with an argument
line that contains the same arguments you would give grep when running
it normally: a grep-style regexp (usually in singlequotes to quote
the shell's special characters) followed by filenames which may use wildcards.
The output from grep goes in the `*compilation*' buffer and the
lines that matched can be found with C-x ` as if they were compilation
errors.
Note: a shell is used to run the compile command, but the shell is told
that it should be noninteractive. This means in particular that the shell
starts up with no prompt. If you find your usual shell prompt making an
unsightly appearance in the `*compilation*' buffer, it means you have
made a mistake in your shell's init file (`.cshrc' or `.shrc' or
...) by setting the prompt unconditionally. The shell init file should
set the prompt only if there already is a prompt. In csh, here is
how to do it:
if ($?prompt) set prompt = ...
Emacs has four different major modes for Lisp. They are the same in terms of editing commands, but differ in the commands for executing Lisp expressions.
Lisp code for Emacs editing commands is stored in files whose names conventionally end in `.el'. This ending tells Emacs to edit them in Emacs-Lisp mode (see section Major Modes for Lisp).
To execute a file of Emacs Lisp, use M-x load-file. This command reads a file name using the minibuffer and then executes the contents of that file as Lisp code. It is not necessary to visit the file first; in any case, this command reads the file as found on disk, not text in an Emacs buffer.
Once a file of Lisp code is installed in the Emacs Lisp library
directories, users can load it using M-x load-library. Programs can
load it by calling load-library, or with load, a more primitive
function that is similar but accepts some additional arguments.
M-x load-library differs from M-x load-file in that it searches a sequence of directories and tries three file names in each directory. The three names are, first, the specified name with `.elc' appended; second, with `.el' appended; third, the specified name alone. A `.elc' file would be the result of compiling the Lisp file into byte code; it is loaded if possible in preference to the Lisp file itself because the compiled file will load and run faster.
Because the argument to load-library is usually not in itself
a valid file name, file name completion is not available. Indeed, when
using this command, you usually do not know exactly what file name
will be used.
The sequence of directories searched by M-x load-library is
specified by the variable load-path, a list of strings that are
directory names. The default value of the list contains the directory where
the Lisp code for Emacs itself is stored. If you have libraries of
your own, put them in a single directory and add that directory
to load-path. nil in this list stands for the current default
directory, but it is probably not a good idea to put nil in the
list. If you find yourself wishing that nil were in the list,
most likely what you really want to do is use M-x load-file
this once.
Often you do not have to give any command to load a library, because the
commands defined in the library are set up to autoload that library.
Running any of those commands causes load to be called to load the
library; this replaces the autoload definitions with the real ones from the
library.
If autoloading a file does not finish, either because of an error or
because of a C-g quit, all function definitions made by the file are
undone automatically. So are any calls to provide. As a consequence,
if you use one of the autoloadable commands again, the entire file will be
loaded a second time. This prevents problems where the command is no
longer autoloading but it works wrong because not all the file was loaded.
Function definitions are undone only for autoloading; explicit calls to
load do not undo anything if loading is not completed.
Emacs Lisp code can be compiled into byte-code which loads faster, takes up less space when loaded, and executes faster.
The way to make a byte-code compiled file from an Emacs-Lisp source file is with M-x byte-compile-file. The default argument for this function is the file visited in the current buffer. It reads the specified file, compiles it into byte code, and writes an output file whose name is made by appending `c' to the input file name. Thus, the file `rmail.el' would be compiled into `rmail.elc'.
To recompile the changed Lisp files in a directory, use M-x byte-recompile-directory. Specify just the directory name as an argument. Each `.el' file that has been byte-compiled before is byte-compiled again if it has changed since the previous compilation. A numeric argument to this command tells it to offer to compile each `.el' file that has not already been compiled. You must answer y or n to each offer.
Emacs can be invoked noninteractively from the shell to do byte compilation
with the aid of the function batch-byte-compile. In this case,
the files to be compiled are specified with command-line arguments.
Use a shell command of the form
emacs -batch -f batch-byte-compile files...
Directory names may also be given as arguments;
byte-recompile-directory is invoked (in effect) on each such directory.
batch-byte-compile uses all the remaining command-line arguments as
file or directory names, then kills the Emacs process.
M-x disassemble explains the result of byte compilation. Its argument is a function name. It displays the byte-compiled code in a help window in symbolic form, one instruction per line. If the instruction refers to a variable or constant, that is shown too.
GNU Emacs can run Mocklisp files by converting them to Emacs Lisp first. To convert a Mocklisp file, visit it and then type M-x convert-mocklisp-buffer. Then save the resulting buffer of Lisp file in a file whose name ends in `.el' and use the new file as a Lisp library.
It does not currently work to byte-compile converted Mocklisp code. This is because converted Mocklisp code uses some special Lisp features to deal with Mocklisp's incompatible ideas of how arguments are evaluated and which values signify "true" or "false".
Lisp programs intended to be run in Emacs should be edited in Emacs-Lisp mode; this will happen automatically for file names ending in `.el'. By contrast, Lisp mode itself is used for editing Lisp programs intended for other Lisp systems. Emacs-Lisp mode can be selected with the command M-x emacs-lisp-mode.
For testing of Lisp programs to run in Emacs, it is useful to be able to evaluate part of the program as it is found in the Emacs buffer. For example, after changing the text of a Lisp function definition, evaluating the definition installs the change for future calls to the function. Evaluation of Lisp expressions is also useful in any kind of editing task for invoking noninteractive functions (functions that are not commands).
eval-expression).
eval-last-sexp).
eval-defun).
M-ESC (eval-expression) is the most basic command for evaluating
a Lisp expression interactively. It reads the expression using the
minibuffer, so you can execute any expression on a buffer regardless of
what the buffer contains. When the expression is evaluated, the current
buffer is once again the buffer that was current when M-ESC was
typed.
M-ESC can easily confuse users who do not understand it,
especially on keyboards with autorepeat where it can result from holding
down the ESC key for too long. Therefore, eval-expression is
normally a disabled command. Attempting to use this command asks for
confirmation and gives you the option of enabling it; once you enable the
command, confirmation will no longer be required for it.
See section Disabling Commands.
In Emacs-Lisp mode, the key C-M-x is bound to the function eval-defun,
which parses the defun containing or following point as a Lisp expression
and evaluates it. The value is printed in the echo area. This command is
convenient for installing in the Lisp environment changes that you have
just made in the text of a function definition.
The command C-x C-e (eval-last-sexp) performs a similar job
but is available in all major modes, not just Emacs-Lisp mode. It finds
the sexp before point, reads it as a Lisp expression, evaluates it, and
prints the value in the echo area. It is sometimes useful to type in an
expression and then, with point still after it, type C-x C-e.
If C-M-x or C-x C-e is given a numeric argument, it prints the value by insertion into the current buffer at point, rather than in the echo area. The argument value does not matter.
The most general command for evaluating Lisp expressions from a buffer is
eval-region. M-x eval-region parses the text of the region as one or
more Lisp expressions, evaluating them one by one. M-x eval-current-buffer
is similar but evaluates the entire buffer. This is a reasonable way to
install the contents of a file of Lisp code that you are just ready to
test. After finding and fixing a bug, use C-M-x on each function
that you change, to keep the Lisp world in step with the source file.
GNU Emacs contains a debugger for Lisp programs executing inside it.
This debugger is normally not used; many commands frequently get Lisp
errors when invoked in inappropriate contexts (such as C-f at the end
of the buffer) and it would be very unpleasant for that to enter a special
debugging mode. When you want to make Lisp errors invoke the debugger, you
must set the variable debug-on-error to non-nil. Quitting
with C-g is not considered an error, and debug-on-error has no
effect on the handling of C-g. However, if you set
debug-on-quit non-nil, C-g will invoke the debugger.
This can be useful for debugging an infinite loop; type C-g once the
loop has had time to reach its steady state. debug-on-quit has no
effect on errors.
You can also cause the debugger to be entered when a specified function
is called, or at a particular place in Lisp code. Use M-x
debug-on-entry with argument fun-name to cause function
fun-name to enter the debugger as soon as it is called. Use
M-x cancel-debug-on-entry to make the function stop entering the
debugger when called. (Redefining the function also does this.) To enter
the debugger from some other place in Lisp code, you must insert the
expression (debug) there and install the changed code with
C-M-x. See section Evaluating Emacs-Lisp Expressions.
When the debugger is entered, it displays the previously selected buffer in one window and a buffer named `*Backtrace*' in another window. The backtrace buffer contains one line for each level of Lisp function execution currently going on. At the beginning of this buffer is a message describing the reason that the debugger was invoked (such as, what error message if it was invoked due to an error).
The backtrace buffer is read-only, and is in a special major mode, Backtrace mode, in which letters are defined as debugger commands. The usual Emacs editing commands are available; you can switch windows to examine the buffer that was being edited at the time of the error, and you can also switch buffers, visit files, and do any other sort of editing. However, the debugger is a recursive editing level (see section Recursive Editing Levels) and it is wise to go back to the backtrace buffer and exit the debugger officially when you don't want to use it any more. Exiting the debugger kills the backtrace buffer.
The contents of the backtrace buffer show you the functions that are executing and the arguments that were given to them. It has the additional purpose of allowing you to specify a stack frame by moving point to the line describing that frame. The frame whose line point is on is considered the current frame. Some of the debugger commands operate on the current frame. Debugger commands are mainly used for stepping through code an expression at a time. Here is a list of them.
wrong-type-argument errors will use the debugger's return value
instead of the invalid argument; no-catch errors will use the
debugger value as a throw tag instead of the tag that was not found.
If an error was signaled by calling the Lisp function signal,
the debugger's return value is returned as the value of signal.
The buffer `*scratch*' which is selected when Emacs starts up is provided for evaluating Lisp expressions interactively inside Emacs. Both the expressions you evaluate and their output goes in the buffer.
The `*scratch*' buffer's major mode is Lisp Interaction mode, which
is the same as Emacs-Lisp mode except for one command, LFD. In
Emacs-Lisp mode, LFD is an indentation command, as usual. In Lisp
Interaction mode, LFD is bound to eval-print-last-sexp. This
function reads the Lisp expression before point, evaluates it, and inserts
the value in printed representation before point.
Thus, the way to use the `*scratch*' buffer is to insert Lisp expressions at the end, ending each one with LFD so that it will be evaluated. The result is a complete typescript of the expressions you have evaluated and their values.
The rationale for this feature is that Emacs must have a buffer when it starts up, but that buffer is not useful for editing files since a new buffer is made for every file that you visit. The Lisp interpreter typescript is the most useful thing I can think of for the initial buffer to do. M-x lisp-interaction-mode will put any buffer in Lisp Interaction mode.
Emacs has facilities for running programs in other Lisp systems. You can run a Lisp process as an inferior of Emacs, and pass expressions to it to be evaluated. You can also pass changed function definitions directly from the Emacs buffers in which you edit the Lisp programs to the inferior Lisp process.
To run an inferior Lisp process, type M-x run-lisp. This runs the
program named lisp, the same program you would run by typing
lisp as a shell command, with both input and output going through an
Emacs buffer named `*lisp*'. That is to say, any "terminal output"
from Lisp will go into the buffer, advancing point, and any "terminal
input" for Lisp comes from text in the buffer. To give input to Lisp, go
to the end of the buffer and type the input, terminated by RET. The
`*lisp*' buffer is in Inferior Lisp mode, a mode which has all the
special characteristics of Lisp mode and Shell mode (see section Shell Mode).
For the source files of programs to run in external Lisps, use Lisp mode. This mode can be selected with M-x lisp-mode, and is used automatically for files whose names end in `.l' or `.lisp', as most Lisp systems usually expect.
When you edit a function in a Lisp program you are running, the easiest
way to send the changed definition to the inferior Lisp process is the key
C-M-x. In Lisp mode, this runs the function lisp-send-defun,
which finds the defun around or following point and sends it as input to
the Lisp process. (Emacs can send input to any inferior process regardless
of what buffer is current.)
Contrast the meanings of C-M-x in Lisp mode (for editing programs to be run in another Lisp system) and Emacs-Lisp mode (for editing Lisp programs to be run in Emacs): in both modes it has the effect of installing the function definition that point is in, but the way of doing so is different according to where the relevant Lisp environment is found. See section Major Modes for Lisp.
An abbrev is a word which expands, if you insert it, into some different text. Abbrevs are defined by the user to expand in specific ways. For example, you might define `foo' as an abbrev expanding to `find outer otter'. With this abbrev defined, you would be able to get `find outer otter ' into the buffer by typing f o o SPC.
Abbrevs expand only when Abbrev mode (a minor mode) is enabled.
Disabling Abbrev mode does not cause abbrev definitions to be forgotten,
but they do not expand until Abbrev mode is enabled again. The command
M-x abbrev-mode toggles Abbrev mode; with a numeric argument, it
turns Abbrev mode on if the argument is positive, off otherwise.
See section Minor Modes. abbrev-mode is also a variable; Abbrev mode is
on when the variable is non-nil. The variable abbrev-mode
automatically becomes local to the current buffer when it is set.
Abbrev definitions can be mode-specific---active only in one major mode. Abbrevs can also have global definitions that are active in all major modes. The same abbrev can have a global definition and various mode-specific definitions for different major modes. A mode specific definition for the current major mode overrides a global definition.
Abbrevs can be defined interactively during the editing session. Lists of abbrev definitions can also be saved in files and reloaded in later sessions. Some users keep extensive lists of abbrevs that they load in every session.
A second kind of abbreviation facility is called the dynamic expansion. Dynamic abbrev expansion happens only when you give an explicit command and the result of the expansion depends only on the current contents of the buffer. See section Dynamic Abbrev Expansion.
add-global-abbrev).
add-mode-abbrev).
inverse-add-global-abbrev).
inverse-add-mode-abbrev).
The usual way to define an abbrev is to enter the text you want the
abbrev to expand to, position point after it, and type C-x +
(add-global-abbrev). This reads the abbrev itself using the
minibuffer, and then defines it as an abbrev for one or more words before
point. Use a numeric argument to say how many words before point should be
taken as the expansion. For example, to define the abbrev `foo' as
mentioned above, insert the text `find outer otter' and then type
C-u 3 C-x + f o o RET.
An argument of zero to C-x + means to use the contents of the region as the expansion of the abbrev being defined.
The command C-x C-a (add-mode-abbrev) is similar, but
defines a mode-specific abbrev. Mode specific abbrevs are active only in a
particular major mode. C-x C-a defines an abbrev for the major mode
in effect at the time C-x C-a is typed. The arguments work the same
as for C-x +.
If the text of the abbrev you want is already in the buffer instead of
the expansion, use command C-x - (inverse-add-global-abbrev)
instead of C-x +, or use C-x C-h
(inverse-add-mode-abbrev) instead of C-x C-a. These commands
are called "inverse" because they invert the meaning of the argument
found in the buffer and the argument read using the minibuffer.
To change the definition of an abbrev, just add the new definition. You will be asked to confirm if the abbrev has a prior definition. To remove an abbrev definition, give a negative argument to C-x + or C-x C-a. You must choose the command to specify whether to kill a global definition or a mode-specific definition for the current mode, since those two definitions are independent for one abbrev.
M-x kill-all-abbrevs removes all the abbrev definitions there are.
An abbrev expands whenever it is present in the buffer just before point and a self-inserting punctuation character (SPC, comma, etc.) is typed. Most often the way an abbrev is used is to insert the abbrev followed by punctuation.
Abbrev expansion preserves case; thus, `foo' expands into `find
outer otter'; `Foo' into `Find outer otter', and `FOO' into
`FIND OUTER OTTER' or `Find Outer Otter' according to the
variable abbrev-all-caps (a non-nil value chooses the first
of the two expansions).
These two commands are used to control abbrev expansion:
abbrev-prefix-mark).
expand-abbrev).
This is effective even when Abbrev mode is not enabled.
You may wish to expand an abbrev with a prefix attached; for example, if
`cnst' expands into `construction', you might want to use it to
enter `reconstruction'. It does not work to type recnst,
because that is not necessarily a defined abbrev. What does work is to use
the command M-' (abbrev-prefix-mark) in between the prefix
`re' and the abbrev `cnst'. First, insert `re'. Then type
M-'; this inserts a minus sign in the buffer to indicate that it has
done its work. Then insert the abbrev `cnst'; the buffer now contains
`re-cnst'. Now insert a punctuation character to expand the abbrev
`cnst' into `construction'. The minus sign is deleted at this
point, because M-' left word for this to be done. The resulting text
is the desired `reconstruction'.
If you actually want the text of the abbrev in the buffer, rather than its expansion, you can accomplish this by inserting the following punctuation with C-q. Thus, foo C-q - leaves `foo-' in the buffer.
If you expand an abbrev by mistake, you can undo the expansion (replace
the expansion by the original abbrev text) with M-x unexpand-abbrev.
C-_ (undo) can also be used to undo the expansion; but first
it will undo the insertion of the following punctuation character!
M-x expand-region-abbrevs searches through the region for defined abbrevs, and for each one found offers to replace it with its expansion. This command is useful if you have typed in text using abbrevs but forgot to turn on Abbrev mode first. It may also be useful together with a special set of abbrev definitions for making several global replacements at once. This command is effective even if Abbrev mode is not enabled.
The output from M-x list-abbrevs looks like this:
(lisp-mode-abbrev-table) "dk" 0 "define-key" (global-abbrev-table) "dfn" 0 "definition"
(Some blank lines of no semantic significance, and some other abbrev tables, have been omitted.)
A line containing a name in parentheses is the header for abbrevs in a
particular abbrev table; global-abbrev-table contains all the global
abbrevs, and the other abbrev tables that are named after major modes
contain the mode-specific abbrevs.
Within each abbrev table, each nonblank line defines one abbrev. The word at the beginning is the abbrev. The number that appears is the number of times the abbrev has been expanded. Emacs keeps track of this to help you see which abbrevs you actually use, in case you decide to eliminate those that you don't use often. The string at the end of the line is the expansion.
M-x edit-abbrevs allows you to add, change or kill abbrev
definitions by editing a list of them in an Emacs buffer. The list has the
same format described above. The buffer of abbrevs is called `*Abbrevs*',
and is in Edit-Abbrevs mode. This mode redefines the key C-c C-c to
install the abbrev definitions as specified in the buffer. The command
that does this is edit-abbrevs-redefine. Any abbrevs not described
in the buffer are eliminated when this is done.
edit-abbrevs is actually the same as list-abbrevs except
that it selects the buffer `*Abbrevs*' whereas list-abbrevs
merely displays it in another window.
These commands allow you to keep abbrev definitions between editing sessions.
M-x write-abbrev-file reads a file name using the minibuffer and writes a description of all current abbrev definitions into that file. The text stored in the file looks like the output of M-x list-abbrevs. This is used to save abbrev definitions for use in a later session.
M-x read-abbrev-file reads a file name using the minibuffer and
reads the file, defining abbrevs according to the contents of the file.
M-x quietly-read-abbrev-file is the same except that it does not
display a message in the echo area saying that it is doing its work; it
is actually useful primarily in the `.emacs' file. If an empty
argument is given to either of these functions, the file name used is the
value of the variable abbrev-file-name, which is by default
"~/.abbrev_defs".
Emacs will offer to save abbrevs automatically if you have changed any of
them, whenever it offers to save all files (for C-x s or C-x
C-c). This feature can be inhibited by setting the variable
save-abbrevs to nil.
The commands M-x insert-abbrevs and M-x define-abbrevs are similar to the previous commands but work on text in an Emacs buffer. M-x insert-abbrevs inserts text into the current buffer before point, describing all current abbrev definitions; M-x define-abbrevs parses the entire current buffer and defines abbrevs accordingly.
The abbrev facility described above operates automatically as you insert text, but all abbrevs must be defined explicitly. By contrast, dynamic abbrevs allow the meanings of abbrevs to be determined automatically from the contents of the buffer, but dynamic abbrev expansion happens only when you request it explicitly.
dabbrev-expand).
For example, if the buffer contains `does this follow ' and you type f o M-/, the effect is to insert `follow' because that is the last word in the buffer that starts with `fo'. A numeric argument to M-/ says to take the second, third, etc. distinct expansion found looking backward from point. Repeating M-/ searches for an alternative expansion by looking farther back. After the entire buffer before point has been considered, the buffer after point is searched.
Dynamic abbrev expansion is completely independent of Abbrev mode; the expansion of a word with M-/ is completely independent of whether it has a definition as an ordinary abbrev.
If you want to create a picture made out of text characters (for example,
a picture of the division of a register into fields, as a comment in a
program), use the command edit-picture to enter Picture mode.
In Picture mode, editing is based on the quarter-plane model of text, according to which the text characters lie studded on an area that stretches infinitely far to the right and downward. The concept of the end of a line does not exist in this model; the most you can say is where the last nonblank character on the line is found.
Of course, Emacs really always considers text as a sequence of characters, and lines really do have ends. But in Picture mode most frequently-used keys are rebound to commands that simulate the quarter-plane model of text. They do this by inserting spaces or by converting tabs to spaces.
Most of the basic editing commands of Emacs are redefined by Picture mode to do essentially the same thing but in a quarter-plane way. In addition, Picture mode defines various keys starting with the C-c prefix to run special picture editing commands.
One of these keys, C-c C-c, is pretty important. Often a picture
is part of a larger file that is usually edited in some other major mode.
M-x edit-picture records the name of the previous major mode, and
then you can use the C-c C-c command (picture-mode-exit) to
restore that mode. C-c C-c also deletes spaces from the ends of
lines, unless given a numeric argument.
The commands used in Picture mode all work in other modes (provided the `picture' library is loaded), but are not bound to keys except in Picture mode. Note that the descriptions below talk of moving "one column" and so on, but all the picture mode commands handle numeric arguments as their normal equivalents do.
Turning on Picture mode calls the value of the variable picture-mode-hook
as a function, with no arguments, if that value exists and is non-nil.
Most keys do the same thing in Picture mode that they usually do, but do
it in a quarter-plane style. For example, C-f is rebound to run
picture-forward-column, which is defined to move point one column to
the right, by inserting a space if necessary, so that the actual end of the
line makes no difference. C-b is rebound to run
picture-backward-column, which always moves point left one column,
converting a tab to multiple spaces if necessary. C-n and C-p
are rebound to run picture-move-down and picture-move-up,
which can either insert spaces or convert tabs as necessary to make sure
that point stays in exactly the same column. C-e runs
picture-end-of-line, which moves to after the last nonblank
character on the line. There is no need to change C-a, as the choice
of screen model does not affect beginnings of lines.
Insertion of text is adapted to the quarter-plane screen model through
the use of Overwrite mode (see section Minor Modes). Self-inserting characters
replace existing text, column by column, rather than pushing existing text
to the right. RET runs picture-newline, which just moves to
the beginning of the following line so that new text will replace that
line.
Deletion and killing of text are replaced with erasure. DEL
(picture-backward-clear-column) replaces the preceding character
with a space rather than removing it. C-d
(picture-clear-column) does the same thing in a forward direction.
C-k (picture-clear-line) really kills the contents of lines,
but does not ever remove the newlines from the buffer.
To do actual insertion, you must use special commands. C-o
(picture-open-line) still creates a blank line, but does so after
the current line; it never splits a line. C-M-o, split-line,
makes sense in Picture mode, so it is not changed. LFD
(picture-duplicate-line) inserts below the current line another line
with the same contents.
Real deletion can be done with C-w, or with C-c C-d (which is
defined as delete-char, as C-d is in other modes), or with one
of the picture rectangle commands (see section Picture Mode Rectangle Commands).
Since "self-inserting" characters in Picture mode just overwrite and move point, there is no essential restriction on how point should be moved. Normally point moves right, but you can specify any of the eight orthogonal or diagonal directions for motion after a "self-inserting" character. This is useful for drawing lines in the buffer.
picture-movement-left).
picture-movement-right).
picture-movement-up).
picture-movement-down).
picture-movement-nw).
picture-movement-ne).
picture-movement-sw).
picture-movement-se).
Two motion commands move based on the current Picture insertion
direction. The command C-c C-f (picture-motion) moves in the
same direction as motion after "insertion" currently does, while C-c
C-b (picture-motion-reverse) moves in the opposite direction.
Two kinds of tab-like action are provided in Picture mode.
Context-based tabbing is done with M-TAB
(picture-tab-search). With no argument, it moves to a point
underneath the next "interesting" character that follows whitespace in
the previous nonblank line. "Next" here means "appearing at a
horizontal position greater than the one point starts out at". With an
argument, as in C-u M-TAB, this command moves to the next such
interesting character in the current line. M-TAB does not
change the text; it only moves point. "Interesting" characters are
defined by the variable picture-tab-chars, which contains a string
whose characters are all considered interesting. Its default value is
"!-~".
TAB itself runs picture-tab, which operates based on the
current tab stop settings; it is the Picture mode equivalent of
tab-to-tab-stop. Normally it just moves point, but with a numeric
argument it clears the text that it moves over.
The context-based and tab-stop-based forms of tabbing are brought
together by the command C-c TAB, picture-set-tab-stops.
This command sets the tab stops to the positions which M-TAB
would consider significant in the current line. The use of this command,
together with TAB, can get the effect of context-based tabbing. But
M-TAB is more convenient in the cases where it is sufficient.
Picture mode defines commands for working on rectangular pieces of the text in ways that fit with the quarter-plane model. The standard rectangle commands may also be useful (see section Rectangles).
picture-clear-rectangle). With
argument, kill it.
picture-clear-rectangle-to-register).
picture-yank-rectangle). With argument,
insert instead.
picture-yank-rectangle-from-register).
The picture rectangle commands C-c C-k
(picture-clear-rectangle) and C-c C-w
(picture-clear-rectangle-to-register) differ from the standard
rectangle commands in that they normally clear the rectangle instead of
deleting it; this is analogous with the way C-d is changed in Picture
mode.
However, deletion of rectangles can be useful in Picture mode, so these commands delete the rectangle if given a numeric argument.
The Picture mode commands for yanking rectangles differ from the standard
ones in overwriting instead of inserting. This is the same way that
Picture mode insertion of other text is different from other modes.
C-c C-y (picture-yank-rectangle) inserts (by overwriting) the
rectangle that was most recently killed, while C-c C-x
(picture-yank-rectangle-from-register) does likewise for the
rectangle found in a specified register.
To send a message in Emacs, you start by typing a command (C-x m) to select and initialize the `*mail*' buffer. Then you edit the text and headers of the message in this buffer, and type another command (C-c C-c) to send the message.
mail).
mail-other-window).
mail-send-and-exit).
The command C-x m (mail) selects a buffer named
`*mail*' and initializes it with the skeleton of an outgoing message.
C-x 4 m (mail-other-window) selects the `*mail*' buffer
in a different window, leaving the previous current buffer visible.
Because the mail composition buffer is an ordinary Emacs buffer, you can switch to other buffers while in the middle of composing mail, and switch back later (or never). If you use the C-x m command again when you have been composing another message but have not sent it, you are asked to confirm before the old message is erased. If you answer n, the `*mail*' buffer is left selected with its old contents, so you can finish the old message and send it. C-u C-x m is another way to do this. Sending the message marks the `*mail*' buffer "unmodified", which avoids the need for confirmation when C-x m is next used.
If you are composing a message in the `*mail*' buffer and want to send another message before finishing the first, rename the `*mail*' buffer using M-x rename-buffer (see section Miscellaneous Buffer Operations).
In addition to the text or contents, a message has header fields which say who sent it, when, to whom, why, and so on. Some header fields such as the date and sender are created automatically after the message is sent. Others, such as the recipient names, must be specified by you in order to send the message properly.
Mail mode provides a few commands to help you edit some header fields, and some are preinitialized in the buffer automatically at times. You can insert or edit any header fields using ordinary editing commands.
The line in the buffer that says
--text follows this line--
is a special delimiter that separates the headers you have specified from
the text. Whatever follows this line is the text of the message; the
headers precede it. The delimiter line itself does not appear in the
message actually sent. The text used for the delimiter line is controlled
by the variable mail-header-separator.
Here is an example of what the headers and text in the `*mail*' buffer might look like.
To: rms@mc CC: mly@mc, rg@oz Subject: The Emacs Manual --Text follows this line-- Please ignore this message.
There are several header fields you can use in the `*mail*' buffer. Each header field starts with a field name at the beginning of a line, terminated by a colon. It does not matter whether you use upper or lower case in the field name. After the colon and optional whitespace comes the contents of the field.
The `To', `CC', `BCC' and `FCC' fields can appear any number of times, to specify many places to send the message.
The `To', `CC', and `BCC' fields can have continuation lines. All the lines starting with whitespace, following the line on which the field starts, are considered part of the field. For example,
To: foo@here, this@there, me@gnu.cambridge.mass.usa.earth.spiral3281
If you have a `~/.mailrc' file, Emacs will scan it for mail aliases the first time you try to send mail in an Emacs session. Aliases found in the `To', `CC', and `BCC' fields will be expanded where appropriate.
If the variable mail-archive-file-name is non-nil, it should be a
string naming a file; every time you start to edit a message to send,
an `FCC' field will be put in for that file. Unless you remove the
`FCC' field, every message will be written into that file when it is
sent.
The major mode used in the `*mail*' buffer is Mail mode, which is much like Text mode except that various special commands are provided on the C-c prefix. These commands all have to do specifically with editing or sending the message.
mail-send).
mail-send-and-exit).
mail-to).
mail-subject).
mail-cc).
mail-signature).
mail-yank-original).
This command does nothing unless your command to start sending a
message was issued with Rmail.
mail-fill-yanked-message).
There are two ways to send the message. C-c C-s (mail-send)
sends the message and marks the `*mail*' buffer unmodified, but leaves
that buffer selected so that you can modify the message (perhaps with new
recipients) and send it again. C-c C-c (mail-send-and-exit)
sends and then deletes the window (if there is another window) or switches
to another buffer. It puts the `*mail*' buffer at the lowest priority
for automatic reselection, since you are finished with using it. This is
the usual way to send the message.
Mail mode provides some other special commands that are useful for
editing the headers and text of the message before you send it. There are
three commands defined to move point to particular header fields, all based
on the prefix C-c C-f (`C-f' is for "field"). They are
C-c C-f C-t (mail-to) to move to the `To' field, C-c
C-f C-s (mail-subject) for the `Subject' field, and C-c
C-f C-c (mail-cc) for the `CC' field. These fields have
special motion commands because they are the most common fields for the
user to want to edit.
C-c C-w (mail-signature) adds a standard piece text at the end of the
message to say more about who you are. The text comes from the file
`.signature' in your home directory.
When mail sending is invoked from the Rmail mail reader using an Rmail command, C-c C-y can be used inside the `*mail*' buffer to insert the text of the message you are replying to. Normally it indents each line of that message four spaces and eliminates most header fields. A numeric argument specifies the number of spaces to indent. An argument of just C-u says not to indent at all and not to eliminate anything. C-c C-y always uses the current message from the `RMAIL' buffer, so you can insert several old messages by selecting one in `RMAIL', switching to `*mail*' and yanking it, then switching back to `RMAIL' to select another.
After using C-c C-y, the command C-c C-q (mail-fill-yanked-message) can
be used to fill the paragraphs of the yanked old message or messages. One
use of C-c C-q fills all such paragraphs, each one separately.
Turning on Mail mode (which C-x m does automatically) calls the
value of text-mode-hook, if it is not void or nil, and then calls
the value of mail-mode-hook if that is not void or nil.
Rmail is an Emacs subsystem for reading and disposing of mail that you receive. Rmail stores mail messages in files called Rmail files. Reading the message in an Rmail file is done in a special major mode, Rmail mode, which redefines most letters to run commands for managing mail. To enter Rmail, type M-x rmail. This reads your primary mail file, merges new mail in from your inboxes, displays the first new message, and lets you begin reading.
Using Rmail in the simplest fashion, you have one Rmail file `~/RMAIL' in which all of your mail is saved. It is called your primary mail file. In more sophisticated usage, you can copy messages into other Rmail files and then edit those files with Rmail.
Rmail displays only one message at a time. It is called the current message. Rmail mode's special commands can do such things as move to another message, delete the message, copy the message into another file, or send a reply.
Within the Rmail file, messages are arranged sequentially in order of receipt. They are also assigned consecutive integers as their message numbers. The number of the current message is displayed in Rmail's mode line, followed by the total number of messages in the file. You can move to a message by specifying its message number using the j key (see section Moving Among Messages).
Following the usual conventions of Emacs, changes in an Rmail file become
permanent only when the file is saved. You can do this with s
(rmail-save), which also expunges deleted messages from the file
first (see section Deleting Messages). To save the file without expunging, use
C-x C-s. Rmail saves the Rmail file spontaneously when moving new
mail from an inbox file (see section Rmail Files and Inboxes).
You can exit Rmail with q (rmail-quit); this expunges and saves the
Rmail file and then switches to another buffer. But there is no need to
`exit' formally. If you switch from Rmail to editing in other buffers, and
never happen to switch back, you have exited. Just make sure to save the
Rmail file eventually (like any other file you have changed). C-x s
is a good enough way to do this (see section Saving Files).
When Rmail displays a message that does not fit on the screen, it is necessary to scroll through it. This could be done with C-v, M-v and M-<, but in Rmail scrolling is so frequent that it deserves to be easier to type.
scroll-up).
scroll-down).
rmail-beginning-of-message).
Since the most common thing to do while reading a message is to scroll
through it by screenfuls, Rmail makes SPC and DEL synonyms of
C-v (scroll-up) and M-v (scroll-down)
The command . (rmail-beginning-of-message) scrolls back to the
beginning of the selected message. This is not quite the same as M-<:
for one thing, it does not set the mark; for another, it resets the buffer
boundaries to the current message if you have changed them.
The most basic thing to do with a message is to read it. The way to do this in Rmail is to make the message current. You can make any message current given its message number using the j command, but the usual thing to do is to move sequentially through the file, since this is the order of receipt of messages. When you enter Rmail, you are positioned at the first new message (new messages are those received since the previous use of Rmail), or at the last message if there are no new messages this time. Move forward to see the other new messages; move backward to reexamine old messages.
rmail-next-undeleted-message).
rmail-previous-undeleted-message).
rmail-next-message).
rmail-previous-message).
rmail-show-message).
rmail-last-message).
rmail-search). If regexp is empty, the last regexp used is
used again.
n and p are the usual way of moving among messages in Rmail. They
move through the messages sequentially, but skip over deleted messages,
which is usually what you want to do. Their command definitions are named
rmail-next-undeleted-message and rmail-previous-undeleted-message. If
you do not want to skip deleted messages--for example, if you want to move
to a message to undelete it--use the variants M-n and M-p
(rmail-next-message and rmail-previous-message). A numeric
argument to any of these commands serves as a repeat count.
In Rmail, you can specify a numeric argument by typing the digits. It is not necessary to type C-u first.
The M-s (rmail-search) command is Rmail's version of search. The
usual incremental search command C-s works in Rmail, but it searches
only within the current message. The purpose of M-s is to search for
another message. It reads a regular expression (see section Syntax of Regular Expressions)
nonincrementally, then searches starting at the beginning of the following
message for a match. The message containing the match is selected.
To search backward in the file for another message, give M-s a negative argument. In Rmail this can be done with - M-s.
It is also possible to search for a message based on labels. See section Labels.
To move to a message specified by absolute message number, use j
(rmail-show-message) with the message number as argument. With no
argument, j selects the first message. > (rmail-last-message) selects
the last message.
When you no longer need to keep a message, you can delete it. This flags it as ignorable, and some Rmail commands will pretend it is no longer present; but it still has its place in the Rmail file, and still has its message number.
Expunging the Rmail file actually removes the deleted messages. The remaining messages are renumbered consecutively. Expunging is the only action that changes the message number of any message, except for undigestifying (see section Digest Messages).
rmail-delete-forward).
rmail-delete-backward).
rmail-undelete-previous-message).
rmail-expunge). These two
commands are synonyms.
There are two Rmail commands for deleting messages. Both delete the
current message and select another message. d (rmail-delete-forward)
moves to the following message, skipping messages already deleted, while
C-d (rmail-delete-backward) moves to the previous nondeleted message.
If there is no nondeleted message to move to in the specified direction,
the message that was just deleted remains current.
To make all the deleted messages finally vanish from the Rmail file,
type e (rmail-expunge). Until you do this, you can still undelete
the deleted messages.
To undelete, type
u (rmail-undelete-previous-message), which is designed to cancel the
effect of a d command (usually). It undeletes the current message
if the current message is deleted. Otherwise it moves backward to previous
messages until a deleted message is found, and undeletes that message.
You can usually undo a d with a u because the u moves back to and undeletes the message that the d deleted. But this does not work when the d skips a few already-deleted messages that follow the message being deleted; then the u command will undelete the last of the messages that were skipped. There is no clean way to avoid this problem. However, by repeating the u command, you can eventually get back to the message that you intended to undelete. You can also reach that message with M-p commands and then type u.
A deleted message has the `deleted' attribute, and as a result `deleted' appears in the mode line when the current message is deleted. In fact, deleting or undeleting a message is nothing more than adding or removing this attribute. See section Labels.
Unix places incoming mail for you in a file that we call your inbox. When you start up Rmail, it copies the new messages from your inbox into your primary mail file, an Rmail file, which also contains other messages saved from previous Rmail sessions. It is in this file that you actually read the mail with Rmail. This operation is called getting new mail. It can be repeated at any time using the g key in Rmail. The inbox file name is `/usr/spool/mail/username' in Berkeley Unix, `/usr/mail/username' in system V.
There are two reason for having separate Rmail files and inboxes.
When getting new mail, Rmail first copies the new mail from the inbox file to the Rmail file; then it saves the Rmail file; then it deletes the inbox file. This way, a system crash may cause duplication of mail between the inbox and the Rmail file, but cannot lose mail.
Copying mail from an inbox in the system's mailer directory actually puts it in an intermediate file `~/.newmail'. This is because the interlocking is done by a C program that copies to another file. `~/.newmail' is deleted after mail merging is successful. If there is a crash at the wrong time, this file will continue to exist and will be used as an inbox the next time you get new mail.
Rmail operates by default on your primary mail file, which is named `~/RMAIL' and receives your incoming mail from your system inbox file. But you can also have other mail files and edit them with Rmail. These files can receive mail through their own inboxes, or you can move messages into them by explicit command in Rmail (see section Copying Messages Out to Files).
rmail-input).
rmail-get-new-mail).
To run Rmail on a file other than your primary mail file, you may use the
i (rmail-input) command in Rmail. This visits the file, puts it in
Rmail mode, and then gets new mail from the file's inboxes if any.
You can also use M-x rmail-input even when not in Rmail.
The file you read with i does not have to be in Rmail file format. It could also be Unix mail format, or mmdf format; or it could be a mixture of all three, as long as each message belongs to one of the three formats. Rmail recognizes all three and converts all the messages to proper Rmail format before showing you the file.
Each Rmail file can contain a list of inbox file names; you can specify this list with M-x set-rmail-inbox-list RET files RET. The argument can contain any number of file names, separated by commas. It can also be empty, which specifies that this file should have no inboxes. Once a list of inboxes is specified, the Rmail file remembers it permanently until it is explicitly changed.
If an Rmail file has inboxes, new mail is merged in from the inboxes when
the Rmail file is brought into Rmail, and when the g (rmail-get-new-mail)
command is used. If the Rmail file specifies no inboxes, then no new mail
is merged in at these times. A special exception is made for your primary
mail file in using the standard system inbox for it if it does not specify
any.
To merge mail from a file that is not the usual inbox, give the g key a numeric argument, as in C-u g. Then it reads a file name and merges mail from that file. The inbox file is not deleted or changed in any way when g with an argument is used. This is, therefore, a general way of merging one file of messages into another.
rmail-output-to-rmail-file).
rmail-output).
If an Rmail file has no inboxes, how does it get anything in it? By explicit o commands.
o (rmail-output-to-rmail-file) appends the current message
in Rmail format to the end of the specified file. This is the best command
to use to move messages between Rmail files. If the other Rmail file is
currently visited, the copying is done into the other file's Emacs buffer
instead. You should eventually save it on disk.
The C-o (rmail-output) command in Rmail appends a copy of the current
message to a specified file, in Unix mail file format. This is useful for
moving messages into files to be read by other mail processors that do not
understand Rmail format.
Copying a message with o or C-o gives the original copy of the message the `filed' attribute, so that `filed' appears in the mode line when such a message is current.
Normally you should use only o to output messages to other Rmail files, never C-o. But it is also safe if you always use C-o, never o. When a file is visited in Rmail, the last message is checked, and if it is in Unix format, the entire file is scanned and all Unix-format messages are converted to Rmail format. (The reason for checking the last message is that scanning the file is slow and most Rmail files have only Rmail format messages.) If you use C-o consistently, the last message is sure to be in Unix format, so Rmail will convert all messages properly.
The case where you might want to use C-o always, instead of o always, is when you or other users want to append mail to the same file from other mail processors. Other mail processors probably do not know Rmail format but do know Unix format.
In any case, always use o to add to an Rmail file that is being visited in Rmail. Adding messages with C-o to the actual disk file will trigger a "simultaneous editing" warning when you ask to save the Emacs buffer, and will be lost if you do save.
Each message can have various labels assigned to it as a means of classification. A label has a name; different names mean different labels. Any given label is either present or absent on a particular message. A few label names have standard meanings and are given to messages automatically by Rmail when appropriate; these special labels are called attributes. All other labels are assigned by the user.
rmail-add-label).
rmail-kill-label).
rmail-next-labeled-message).
rmail-previous-labeled-message).
rmail-summary-by-labels).
Specifying an empty string for one these commands means to use the last label specified for any of these commands.
The a (rmail-add-label) and k (rmail-kill-label) commands allow
you to assign or remove any label on the current message. If the label
argument is empty, it means to assign or remove the same label most
recently assigned or removed.
Once you have given messages labels to classify them as you wish, there are two ways to use the labels: in moving and in summaries.
The command C-M-n labels RET
(rmail-next-labeled-message) moves to the next message that has one
of the labels labels. labels is one or more label names,
separated by commas. C-M-p (rmail-previous-labeled-message)
is similar, but moves backwards to previous messages. A preceding numeric
argument to either one serves as a repeat count.
The command C-M-l labels RET
(rmail-summary-by-labels) displays a summary containing only the
messages that have at least one of a specified set of messages. The
argument labels is one or more label names, separated by commas.
See section Summaries, for information on summaries.
If the labels argument to C-M-n, C-M-p or C-M-l is empty, it means to use the last set of labels specified for any of these commands.
Some labels such as `deleted' and `filed' have built-in meanings and are assigned to or removed from messages automatically at appropriate times; these labels are called attributes. Here is a list of Rmail attributes:
rmail-reply). See section Sending Replies.
rmail-forward). See section Sending Replies.
All other labels are assigned or removed only by the user, and it is up to the user to decide what they mean.
A summary is a buffer containing one line per message that Rmail can make and display to give you an overview of the mail in an Rmail file. Each line shows the message number, the sender, the labels, and the subject. When the summary buffer is selected, various commands can be used to select messages by moving in the summary buffer, or delete or undelete messages.
A summary buffer applies to a single Rmail file only; if you are editing multiple Rmail files, they have separate summary buffers. The summary buffer name is made by appending `-summary' to the Rmail buffer's name. Only one summary buffer will be displayed at a time unless you make several windows and select the summary buffers by hand.
Here are the commands to create a summary for the current Rmail file. Summaries do not update automatically; to make an updated summary, you must use one of these commands again.
rmail-summary).
rmail-summary-by-labels).
rmail-summary-by-recipients)
The h or C-M-h (rmail-summary) command fills the summary buffer
for the current Rmail file with a summary of all the messages in the file.
It then displays and selects the summary buffer in another window.
C-M-l labels RET (rmail-summary-by-labels) makes
a partial summary mentioning only the messages that have one or more of the
labels labels. labels should contain label names separated by
commas.
C-M-r rcpts RET (rmail-summary-by-recipients)
makes a partial summary mentioning only the messages that have one or more
of the recipients rcpts. rcpts should contain mailing
addresses separated by commas.
Note that there is only one summary buffer for any Rmail file; making one kind of summary discards any previously made summary.
Summary buffers are given the major mode Rmail Summary mode, which provides the following special commands:
rmail-summary-goto-msg).
rmail-summary-next-all).
rmail-summary-previous-all).
rmail-summary-next-msg).
rmail-summary-previous-msg).
rmail-summary-delete-forward).
rmail-summary-undelete).
rmail-summary-scroll-msg-up).
rmail-summary-scroll-msg-down).
rmail-summary-exit).
rmail-summary-quit).
The keys C-n and C-p are modified in Rmail Summary mode so that in addition to moving point in the summary buffer they also cause the line's message to become current in the associated Rmail buffer. That buffer is also made visible in another window if it is not already so.
n and p are similar to C-n and C-p, but skip lines that say `message deleted'. They are like the n and p keys of Rmail itself. Note, however, that in a partial summary these commands move only among the message listed in the summary.
The other Emacs cursor motion commands are not changed in Rmail Summary
mode, so it is easy to get the point on a line whose message is not
selected in Rmail. This can also happen if you switch to the Rmail window
and switch messages there. To get the Rmail buffer back in sync with the
summary, use the j (rmail-summary-goto-msg) command, which selects
in Rmail the message of the current summary line.
Deletion and undeletion can also be done from the summary buffer. They
always work based on where point is located in the summary buffer, ignoring
which message is selected in Rmail. d (rmail-summary-delete-forward)
deletes the current line's message, then moves to the next line whose
message is not deleted and selects that message. The inverse of this is
u (rmail-summary-undelete), which moves back (if necessary) to a line
whose message is deleted, undeletes that message, and selects it in Rmail.
When moving through messages with the summary buffer, it is convenient to
be able to scroll the message while remaining in the summary window.
The commands SPC (rmail-summary-scroll-msg-up) and DEL
(rmail-summary-scroll-msg-down) do this. They scroll the message just
as those same keys do when the Rmail buffer is selected.
When you are finished using the summary, type x (rmail-summary-exit)
to kill the summary buffer's window.
You can also exit Rmail while in the summary. q (rmail-summary-quit)
kills the summary window, then saves the Rmail file and switches to another
buffer.
Rmail has several commands that use Mail mode to send outgoing mail. See section Sending Mail, for information on using Mail mode. What are documented here are the special commands of Rmail for entering Mail mode. Note that the usual keys for sending mail, C-x m and C-x 4 m, are available in Rmail mode and work just as they usually do.
rmail-mail).
rmail-continue).
rmail-reply).
rmail-forward).
The most common reason to send a message while in Rmail is to reply to
the message you are reading. To do this, type r
(rmail-reply). This displays the `*mail*' buffer in another
window, much like C-x 4 m, but preinitializes the `Subject',
`To', `CC' and `In-reply-to' header fields based on the
message being replied to. The `To' field is given the sender of that
message, and the `CC' gets all the recipients of that message (but
recipients that match elements of the list rmail-dont-reply-to are
omitted; by default, this list contains your own mailing address).
Once you have initialized the `*mail*' buffer this way, sending the mail goes as usual (see section Sending Mail). You can edit the presupplied header fields if they are not right for you.
One additional Mail mode command is available when mailing is invoked
from Rmail: C-c C-y (mail-yank-original) inserts into the outgoing
message a copy of the current Rmail message; normally this is the message
you are replying to, but you can also switch to the Rmail buffer, select a
different message, switch back, and yank new current message. Normally the
yanked message is indented four spaces and has most header fields deleted
from it; an argument to C-c C-y specifies the amount to indent, and
C-u C-c C-y does not indent at all and does not delete any header
fields.
Another frequent reason to send mail in Rmail is to forward the current
message to other users. f (rmail-forward) makes this easy by
preinitializing the `*mail*' buffer with the current message as the
text, and a subject designating a forwarded message. All you have to do is
fill in the recipients and send.
The m (rmail-mail) command is used to start editing an
outgoing message that is not a reply. It leaves the header fields empty.
Its only difference from C-x 4 m is that it makes the Rmail buffer
accessible for C-c y, just as r does. Thus, m can be
used to reply to or forward a message; it can do anything r or f
can do.
The c (rmail-continue) command resumes editing the
`*mail*' buffer, to finish editing an outgoing message you were
already composing, or to alter a message you have sent.
Rmail mode provides a few special commands for moving within and editing the current message. In addition, the usual Emacs commands are available (except for a few, such as C-M-n and C-M-h, that are redefined by Rmail for other purposes). However, the Rmail buffer is normally read-only, and to alter it you must use the Rmail command w described below.
rmail-toggle-headers).
rmail-edit-current-message).
Rmail reformats the header of each message before displaying it.
Normally this involves deleting most header fields, on the grounds that
they are not interesting. The variable rmail-ignored-headers should
contain a regexp that matches the header fields to discard in this way.
The original headers are saved permanently, and to see what they look like,
use the t (rmail-toggle-headers) command. This discards the reformatted
headers of the current message and displays it with the original headers.
Repeating t reformats the message again. Selecting the message again
also reformats.
The Rmail buffer is normally read only, and most of the characters you
would type to modify it (including most letters) are redefined as Rmail
commands. This is usually not a problem since it is rare to want to change
the text of a message. When you do want to do this, the way is to type
w (rmail-edit-current-message), which changes from Rmail mode into
Rmail Edit mode, another major mode which is nearly the same as Text mode.
The mode line illustrates this change.
In Rmail Edit mode, letters insert themselves as usual and the Rmail commands are not available. When you are finished editing the message and are ready to go back to Rmail, type C-c C-c, which switches back to Rmail mode. Alternatively, you can return to Rmail mode but cancel all the editing that you have done by typing C-c C-].
Entering Rmail Edit mode calls with no arguments the value of the variable
text-mode-hook, if that value exists and is not nil; then it
does the same with the variable rmail-edit-mode-hook. It adds the
attribute `edited' to the message.
A digest message is a message which exists to contain and carry several other messages. Digests are used on moderated mailing lists; all the messages that arrive for the list during a period of time such as one day are put inside a single digest which is then sent to the subscribers. Transmitting the single digest uses much less computer time than transmitting the individual messages even though the total size is the same, because the per-message overhead in network mail transmission is considerable.
When you receive a digest message, the most convenient way to read it is to undigestify it: to turn it back into many individual messages. Then you can read and delete the individual messages as it suits you.
To undigestify a message, select it and then type M-x undigestify-rmail-message. This copies each submessage as a separate Rmail message and inserts them all following the digest. The digest message itself is flagged as deleted.
This chapter contains several brief topics that do not fit anywhere else.
A recursive edit is a situation in which you are using Emacs
commands to perform arbitrary editing while in the middle of another Emacs
command. For example, when you type C-r inside of a query-replace,
you enter a recursive edit in which you can change the current buffer. On
exiting from the recursive edit, you go back to the query-replace.
Exiting the recursive edit means returning to the unfinished
command, which continues execution. For example, exiting the recursive
edit requested by C-r in query-replace causes query replacing
to resume. Exiting is done with C-M-c (exit-recursive-edit).
You can also abort the recursive edit. This is like exiting, but
also quits the unfinished command immediately. Use the command C-]
(abort-recursive-edit) for this. See section Quitting and Aborting.
The mode line shows you when you are in a recursive edit by displaying square brackets around the parentheses that always surround the major and minor mode names. Every window's mode line shows this, in the same way, since being in a recursive edit is true of Emacs as a whole rather than any particular buffer.
It is possible to be in recursive edits within recursive edits. For
example, after typing C-r in a query-replace, you might type a
command that entered the debugger. In such circumstances, two or more sets
of square brackets appear in the mode line. Exiting the inner recursive
edit (such as, with the debugger c command) would resume the command
where it called the debugger. After the end of this command, you would be
able to exit the first recursive edit. Aborting also gets out of only one
level of recursive edit; it returns immediately to the command level of the
previous recursive edit. So you could immediately abort that one too.
Alternatively, the command M-x top-level aborts all levels of recursive edits, returning immediately to the top level command reader.
The text being edited inside the recursive edit need not be the same text that you were editing at top level. It depends on what the recursive edit is for. If the command that invokes the recursive edit selects a different buffer first, that is the buffer you will edit recursively. In any case, you can switch buffers within the recursive edit in the normal manner (as long as the buffer-switching keys have not been rebound). You could probably do all the rest of your editing inside the recursive edit, visiting files and all. But this could have surprising effects (such as stack overflow) from time to time. So remember to exit or abort the recursive edit when you no longer need it.
In general, GNU Emacs tries to avoid using recursive edits. It is usually preferable to allow the user to switch among the possible editing modes in any order he likes. With recursive edits, the only way to get to another state is to go "back" to the state that the recursive edit was invoked from.
Narrowing means focusing in on some portion of the buffer, making the rest temporarily invisible and inaccessible. Cancelling the narrowing, and making the entire buffer once again visible, is called widening. The amount of narrowing in effect in a buffer at any time is called the buffer's restriction.
narrow-to-region).
widen).
When you have narrowed down to a part of the buffer, that part appears to be all there is. You can't see the rest, you can't move into it (motion commands won't go outside the visible part), you can't change it in any way. However, it is not gone, and if you save the file all the invisible text will be saved. In addition to sometimes making it easier to concentrate on a single subroutine or paragraph by eliminating clutter, narrowing can be used to restrict the range of operation of a replace command or repeating keyboard macro. The word `Narrow' appears in the mode line whenever narrowing is in effect.
The primary narrowing command is C-x n (narrow-to-region).
It sets the current buffer's restrictions so that the text in the current
region remains visible but all text before the region or after the region
is invisible. Point and mark do not change.
Because narrowing can easily confuse users who do not understand it,
narrow-to-region is normally a disabled command. Attempting to use
this command asks for confirmation and gives you the option of enabling it;
once you enable the command, confirmation will no longer be required for
it. See section Disabling Commands.
The way to undo narrowing is to widen with C-x w (widen).
This makes all text in the buffer accessible again.
You can get information on what part of the buffer you are narrowed down to using the C-x = command. See section Cursor Position Information.
Emacs provides several commands for sorting text in the buffer. All operate on the contents of the region (the text between point and the mark). They divide the text of the region into many sort records, identify a sort key for each record, and then reorder the records into the order determined by the sort keys. The records are ordered so that their keys are in alphabetical order, or, for numeric sorting, in numeric order. In alphabetic sorting, all upper case letters `A' through `Z' come before lower case `a', in accord with the ASCII character sequence.
The various sort commands differ in how they divide the text into sort records and in which part of each record is used as the sort key. Most of the commands make each line a separate sort record, but some commands use paragraphs or pages as sort records. Most of the sort commands use each entire sort record as its own sort key, but some use only a portion of the record as the sort key.
For example, if the buffer contains
On systems where clash detection (locking of files being edited) is implemented, Emacs also checks the first time you modify a buffer whether the file has changed on disk since it was last visited or saved. If it has, you are asked to confirm that you want to change the buffer.
then if you apply M-x sort-lines to the entire buffer you get
On systems where clash detection (locking of files being edited) is implemented, Emacs also checks the first time you modify a buffer saved. If it has, you are asked to confirm that you want to change the buffer. whether the file has changed on disk since it was last visited or
where the upper case `O' comes before all lower case letters. If you apply instead C-u 2 M-x sort-fields you get
implemented, Emacs also checks the first time you modify a buffer saved. If it has, you are asked to confirm that you want to change the buffer. On systems where clash detection (locking of files being edited) is whether the file has changed on disk since it was last visited or
where the sort keys were `Emacs', `If', `buffer', `systems' and `the'.
M-x sort-columns requires more explanation. You specify the columns by putting point at one of the columns and the mark at the other column. Because this means you cannot put point or the mark at the beginning of the first line to sort, this command uses an unusual definition of `region': all of the line point is in is considered part of the region, and so is all of the line the mark is in.
For example, to sort a table by information found in columns 10 to 15, you could put the mark on column 10 in the first line of the table, and point on column 15 in the last line of the table, and then use this command. Or you could put the mark on column 15 in the first line and point on column 10 in the last line.
This can be thought of as sorting the rectangle specified by point and the mark, except that the text on each line to the left or right of the rectangle moves along with the text inside the rectangle. See section Rectangles.
Emacs has commands for passing single command lines to inferior shell processes; it can also run a shell interactively with input and output to an Emacs buffer `*shell*'.
shell-command).
shell-command-on-region).
M-! (shell-command) reads a line of text using the
minibuffer and creates an inferior shell to execute the line as a command.
Standard input from the command comes from the null device. If the shell
command produces any output, the output goes into an Emacs buffer named
`*Shell Command Output*', which is displayed in another window but not
selected. A numeric argument, as in M-1 M-!, directs this command to
insert any output into the current buffer. In that case, point is left
before the output and the mark is set after the output.
M-| (shell-command-on-region) is like M-! but passes
the contents of the region as input to the shell command, instead of no
input. If a numeric argument is used, meaning insert output in the current
buffer, then the old region is deleted first and the output replaces it as
the contents of the region.
Both M-! and M-| use shell-file-name to specify the
shell to use. This variable is initialized based on your SHELL
environment variable when Emacs is started. If the file name does not
specify a directory, the directories in the list exec-path are
searched; this list is initialized based on the environment variable
PATH when Emacs is started. Your `.emacs' file can override
either or both of these default initializations.
With M-! and M-|, Emacs has to wait until the shell command completes. You can quit with C-g; that terminates the shell command.
To run a subshell interactively, putting its typescript in an Emacs buffer, use M-x shell. This creates (or reuses) a buffer named `*shell*' and runs a subshell with input coming from and output going to that buffer. That is to say, any "terminal output" from the subshell will go into the buffer, advancing point, and any "terminal input" for the subshell comes from text in the buffer. To give input to the subshell, go to the end of the buffer and type the input, terminated by RET.
Emacs does not wait for the subshell to do anything. You can switch windows or buffers and edit them while the shell is waiting, or while it is running a command. Output from the subshell waits until Emacs has time to process it; this happens whenever Emacs is waiting for keyboard input or for time to elapse.
If you would like multiple subshells, change the name of buffer `*shell*' to something different by using M-x rename-buffer. The next use of M-x shell will create a new buffer `*shell*' with its own subshell. By renaming this buffer as well you can create a third one, and so on. All the subshells run independently and in parallel.
The file name used to load the subshell is the value of the variable
explicit-shell-file-name, if that is non-nil. Otherwise, the
environment variable ESHELL is used, or the environment variable
SHELL if there is no ESHELL. If the file name specified
is relative, the directories in the list exec-path are searched
(see section Single Shell Commands).
As soon as the subshell is started, it is sent as input the contents of
the file `~/.emacs_shellname', if that file exists, where
shellname is the name of the file that the shell was loaded from.
For example, if you use csh, the file sent to it is
`~/.emacs_csh'.
cd, pushd and popd commands given to the inferior
shell are watched by Emacs so it can keep the `*shell*' buffer's
default directory the same as the shell's working directory. These
commands are recognized syntactically by examining lines of input that are
sent. If you use aliases for these commands, you can tell Emacs to
recognize them also. For example, if the value of the variable
shell-pushd-regexp matches the beginning of a shell command line,
that line is regarded as a pushd command. Change this variable when
you add aliases for `pushd'. Likewise, shell-popd-regexp and
shell-cd-regexp are used to recognize commands with the meaning of
`popd' and `cd'. These commands are recognized only at the
beginning of a shell command line.
If Emacs gets an error while trying to handle what it believes is
a `cd', `pushd' or `popd' command, and the value of
shell-set-directory-error-hook is non-nil, that value is
called as a function with no arguments.
The shell buffer uses Shell mode, which defines several special keys attached to the C-c prefix. They are chosen to resemble the usual editing and job control characters present in shells that are not under Emacs, except that you must type C-c first. Here is a complete list of the special key bindings of Shell mode:
send-shell-input). When a line is copied, any
text at the beginning of the line that matches the variable
shell-prompt-pattern is left out; this variable's value should be a
regexp string that matches the prompts that you use in your subshell.
shell-send-eof).
kill-shell-input).
backward-kill-word).
interrupt-shell-subjob).
stop-shell-subjob).
quit-shell-subjob).
kill-output-from-shell).
show-output-from-shell).
copy-last-shell-input). No final newline
is inserted, and the input copied is not resubmitted until you type
RET.
The Emacs commands for making hardcopy derive their names from the Unix commands `print' and `lpr'.
print-buffer but prints only the current region.
lpr-buffer but prints only the current region.
All the hardcopy commands pass extra switches to the lpr program
based on the value of the variable lpr-switches. Its value should
be a list of strings, each string a switch starting with `-'. For
example, the value could be ("-Pfoo") to print on printer
`foo'.
M-x dissociated-press is a command for scrambling a file of text either word by word or character by character. Starting from a buffer of straight English, it produces extremely amusing output. The input comes from the current Emacs buffer. Dissociated Press writes its output in a buffer named `*Dissociation*', and redisplays that buffer after every couple of lines (approximately) to facilitate reading it.
dissociated-press asks every so often whether to continue
operating. Answer n to stop it. You can also stop at any time by
typing C-g. The dissociation output remains in the `*Dissociation*'
buffer for you to copy elsewhere if you wish.
Dissociated Press operates by jumping at random from one point in the buffer to another. In order to produce plausible output rather than gibberish, it insists on a certain amount of overlap between the end of one run of consecutive words or characters and the start of the next. That is, if it has just printed out `president' and then decides to jump to a different point in the file, it might spot the `ent' in `pentagon' and continue from there, producing `presidentagon'. Long sample texts produce the best results.
A positive argument to M-x dissociated-press tells it to operate character by character, and specifies the number of overlap characters. A negative argument tells it to operate word by word and specifies the number of overlap words. In this mode, whole words are treated as the elements to be permuted, rather than characters. No argument is equivalent to an argument of two. For your againformation, the output goes only into the buffer `*Dissociation*'. The buffer you start with is not changed.
Dissociated Press produces nearly the same results as a Markov chain based on a frequency table constructed from the sample text. It is, however, an independent, ignoriginal invention. Dissociated Press techniquitously copies several consecutive characters from the sample between random choices, whereas a Markov chain would choose randomly for each word or character. This makes for more plausible sounding results, and runs faster.
It is a mustatement that too much use of Dissociated Press can be a developediment to your real work. Sometimes to the point of outragedy. And keep dissociwords out of your documentation, if you want it to be well userenced and properbose. Have fun. Your buggestions are welcome.
If you are a little bit bored, you can try M-x hanoi. If you are considerably bored, give it a numeric argument. If you are very very bored, try an argument of 9. Sit back and watch.
When you are frustrated, try the famous Eliza program. Just do M-x doctor. End each input by typing RET twice.
When you are feeling strange, type M-x yow.
GNU Emacs can be programmed to emulate (more or less) most other editors. Standard facilities can emulate these:
vi-mode command.
vip-mode as
it is with vi-mode because terminating insert mode does
not use it.
For full information, see the long comment at the beginning of the
source file, which is `lisp/vip.el' in the Emacs distribution.
I am interested in hearing which vi emulator users prefer, as well as in receiving more complete user documentation for either or both emulators. Warning: loading both at once may cause name conficts; no one has checked.
This chapter talks about various topics relevant to adapting the behavior of Emacs in minor ways.
All kinds of customization affect only the particular Emacs job that you do them in. They are completely lost when you kill the Emacs job, and have no effect on other Emacs jobs you may run at the same time or later. The only way an Emacs job can affect anything outside of it is by writing a file; in particular, the only way to make a customization `permanent' is to put something in your `.emacs' file or other appropriate file to do the customization in each session. See section The Init File, .emacs.
Minor modes are options which you can use or not. For example, Auto Fill mode is a minor mode in which SPC breaks lines between words as you type. All the minor modes are independent of each other and of the selected major mode. Most minor modes say in the mode line when they are on; for example, `Fill' in the mode line means that Auto Fill mode is on.
Append -mode to the name of a minor mode to get the name of a
command function that turns the mode on or off. Thus, the command to
enable or disable Auto Fill mode is called M-x auto-fill-mode. These
commands are usually invoked with M-x, but you can bind keys to them
if you wish. With no argument, the function turns the mode on if it was
off and off if it was on. This is known as toggling. A positive
argument always turns the mode on, and an explicit zero argument or a
negative argument always turns it off.
Auto Fill mode allows you to enter filled text without breaking lines explicitly. Emacs inserts newlines as necessary to prevent lines from becoming too long. See section Filling Text.
Overwrite mode causes ordinary printing characters to replace existing text instead of shoving it over. For example, if the point is in front of the `B' in `FOOBAR', then in Overwrite mode typing a G changes it to `FOOGAR', instead of making it `FOOGBAR' as usual.
Abbrev mode allows you to define abbreviations that automatically expand as you type them. For example, `amd' might expand to `abbrev mode'. See section Abbrevs, for full information.
A variable is a Lisp symbol which has a value. The symbol's name is also called the name of the variable. Variable names can contain any characters, but conventionally they are chosen to be words separated by hyphens. A variable can have a documentation string which describes what kind of value it should have and how the value will be used.
Lisp allows any variable to have any kind of value, but most variables
that Emacs uses require a value of a certain type. Often the value should
always be a string, or should always be a number. Sometimes we say that a
certain feature is turned on if a variable is "non-nil," meaning
that if the variable's value is nil, the feature is off, but the
feature is on for any other value. The conventional value to use to
turn on the feature--since you have to pick one particular value when you
set the variable--is t.
Emacs uses many Lisp variables for internal recordkeeping, as any Lisp program must, but the most interesting variables for you are the ones that exist for the sake of customization. Emacs does not (usually) change the values of these variables; instead, you set the values, and thereby alter and control the behavior of certain Emacs commands. These variables are called options. Most options are documented in this manual, and appear in the Variable Index (see section Variable Index).
One example of a variable which is an option is fill-column, which
specifies the position of the right margin (as a number of characters from
the left margin) to be used by the fill commands (see section Filling Text).
To examine the value of a single variable, use C-h v
(describe-variable), which reads a variable name using the
minibuffer, with completion. It prints both the value and the
documentation of the variable.
C-h v fill-column RET
prints something like
fill-column's value is 75 Documentation: *Column beyond which automatic line-wrapping should happen. Automatically becomes local when set in any fashion.
The star at the beginning of the documentation indicates that this variable is an option. C-h v is not restricted to options; it allows any variable name.
If you know which option you want to set, you can set it using M-x set-variable. This reads the variable name with the minibuffer (with completion), and then reads a Lisp expression for the new value using the minibuffer a second time. For example,
M-x set-variable RET fill-column RET 75 RET
sets fill-column to 75, like executing the Lisp expression
(setq fill-column 75)
Setting variables in this way, like all means of customizing Emacs except where explicitly stated, affects only the current Emacs session.
M-x list-options displays a list of all Emacs option variables, in an Emacs buffer named `*List Options*'. Each option is shown with its documentation and its current value. Here is what a portion of it might look like:
;; exec-path:
("." "/usr/local/bin" "/usr/ucb" "/bin" "/usr/bin" "/u2/emacs/etc")
*List of directories to search programs to run in subprocesses.
Each element is a string (directory name)
or nil (try the default directory).
;;
;; fill-column:
75
*Column beyond which automatic line-wrapping should happen.
Automatically becomes local when set in any fashion.
;;
M-x edit-options goes one step further and immediately selects the `*List Options*' buffer; this buffer uses the major mode Options mode, which provides commands that allow you to point at an option and change its value:
nil,
it becomes t; otherwise it becomes nil.
t.
nil.
Any variable can be made local to a specific Emacs buffer. This means that its value in that buffer is independent of its value in other buffers. A few variables are always local in every buffer. Every other Emacs variable has a global value which is in effect in all buffers that have not made the variable local.
Major modes always make the variables they set local to the buffer. This is why changing major modes in one buffer has no effect on other buffers.
M-x make-local-variable reads the name of a variable and makes it local to the current buffer. Further changes in this buffer will not affect others, and further changes in the global value will not affect this buffer.
M-x make-variable-buffer-local reads the name of a variable and
changes the future behavior of the variable so that it will become local
automatically when it is set. More precisely, once a variable has been
marked in this way, the usual ways of setting the variable will
automatically do make-local-variable first. We call such variables
per-buffer variables.
Some important variables have been marked per-buffer already. These include
abbrev-mode, auto-fill-hook, case-fold-search,
comment-column, ctl-arrow, fill-column,
fill-prefix, indent-tabs-mode, left-margin,
mode-line-format, overwrite-mode,
selective-display-ellipses, selective-display,
tab-width, and truncate-lines. Some other variables are
always local in every buffer, but they are used for internal purposes.
M-x kill-local-variable reads the name of a variable and makes it cease to be local to the current buffer. The global value of the variable henceforth is in effect in this buffer. Setting the major mode kills all the local variables of the buffer.
To set the global value of a variable, regardless of whether the
variable has a local value in the current buffer, you can use the
Lisp function setq-default. It works like setq.
If there is a local value in the current buffer, the local value is
not affected by setq-default; thus, the new global value may
not be visible until you switch to another buffer. For example,
(setq-default fill-column 75)
setq-default is the only way to set the global value of a variable
that has been marked with make-variable-buffer-local.
Programs can look at a variable's default value with default-value.
This function takes a symbol as argument and returns its default value.
The argument is evaluated; usually you must quote it explicitly. For
example,
(default-value 'fill-column)
A file can contain a local variables list, which specifies the values to use for certain Emacs variables when that file is edited. Visiting the file checks for a local variables list and makes each variable in the list local to the buffer in which the file is visited, with the value specified in the file.
A local variables list goes near the end of the file, in the last page. (It is often best to put it on a page by itself.) The local variables list starts with a line containing the string `Local Variables:', and ends with a line containing the string `End:'. In between come the variable names and values, one set per line, as `variable: value'. The values are not evaluated; they are used literally.
The line which starts the local variables list does not have to say just `Local Variables:'. If there is other text before `Local Variables:', that text is called the prefix, and if there is other text after, that is called the suffix. If these are present, each entry in the local variables list should have the prefix before it and the suffix after it. This includes the `End:' line. The prefix and suffix are included to disguise the local variables list as a comment so that the compiler or text formatter will not be perplexed by it. If you do not need to disguise the local variables list as a comment in this way, do not bother with a prefix or a suffix.
Two "variable" names are special in a local variables list: a value for
the variable mode really sets the major mode, and a value for the
variable eval is simply evaluated as an expression and the value is
ignored. These are not real variables; setting such variables in any other
context has no such effect. If mode is used in a local variables
list, it should be the first entry in the list.
Here is an example of a local variables list:
;;; Local Variables: *** ;;; mode:lisp *** ;;; comment-column:0 *** ;;; comment-start: ";;; " *** ;;; comment-end:"***" *** ;;; End: ***
Note that the prefix is `;;; ' and the suffix is ` ***'. Note also that comments in the file begin with and end with the same strings. Presumably the file contains code in a language which is like Lisp (like it enough for Lisp mode to be useful) but in which comments start and end in that way. The prefix and suffix are used in the local variables list to make the list appear as comments when the file is read by the compiler or interpreter for that language.
The start of the local variables list must be no more than 3000 characters from the end of the file, and must be in the last page if the file is divided into pages. Otherwise, Emacs will not notice it is there. The purpose of this is so that a stray `Local Variables:' not in the last page does not confuse Emacs, and so that visiting a long file that is all one page and has no local variables list need not take the time to search the whole file.
You may be tempted to try to turn on Auto Fill mode with a local variable list. That is a mistake. The choice of Auto Fill mode or not is a matter of individual taste, not a matter of the contents of particular files. If you want to use Auto Fill, set up major mode hooks with your `.emacs' file to turn it on (when appropriate) for you alone (see section The Init File, .emacs). Don't try to use a local variable list that would impose your taste on everyone.
A keyboard macro is a command defined by the user to abbreviate a sequence of keys. For example, if you discover that you are about to type C-n C-d forty times, you can speed your work by defining a keyboard macro to do C-n C-d and calling it with a repeat count of forty.
start-kbd-macro).
end-kbd-macro).
call-last-kbd-macro).
kbd-macro-query).
Keyboard macros differ from ordinary Emacs commands in that they are written in the Emacs command language rather than in Lisp. This makes it easier for the novice to write them, and makes them more convenient as temporary hacks. However, the Emacs command language is not powerful enough as a programming language to be useful for writing anything intelligent or general. For such things, Lisp must be used.
You define a keyboard macro while executing the commands which are the definition. Put differently, as you are defining a keyboard macro, the definition is being executed for the first time. This way, you can see what the effects of your commands are, so that you don't have to figure them out in your head. When you are finished, the keyboard macro is defined and also has been, in effect, executed once. You can then do the whole thing over again by invoking the macro.
To start defining a keyboard macro, type the C-x ( command
(start-kbd-macro). From then on, your keys continue to be
executed, but also become part of the definition of the macro. `Def'
appears in the mode line to remind you of what is going on. When you are
finished, the C-x ) command (end-kbd-macro) terminates the
definition (without becoming part of it!). For example
C-x ( M-F foo C-x )
defines a macro to move forward a word and then insert `foo'.
The macro thus defined can be invoked again with the C-x e command
(call-last-kbd-macro), which may be given a repeat count as a
numeric argument to execute the macro many times. C-x ) can also be
given a repeat count as an argument, in which case it repeats the macro
that many times right after defining it, but defining the macro counts as
the first repetition (since it is executed as you define it). So, giving
C-x ) an argument of 4 executes the macro immediately 3 additional
times. An argument of zero to C-x e or C-x ) means repeat the
macro indefinitely (until it gets an error or you type C-g).
If you wish to repeat an operation at regularly spaced places in the text, define a macro and include as part of the macro the commands to move to the next place you want to use it. For example, if you want to change each line, you should position point at the start of a line, and define a macro to change that line and leave point at the start of the next line. Then repeating the macro will operate on successive lines.
After you have terminated the definition of a keyboard macro, you can add to the end of its definition by typing C-u C-x (. This is equivalent to plain C-x ( followed by retyping the whole definition so far. As a consequence it re-executes the macro as previously defined.
If you wish to save a keyboard macro for longer than until you define the
next one, you must give it a name using M-x name-last-kbd-macro.
This reads a name as an argument using the minibuffer and defines that name
to execute the macro. The macro name is a Lisp symbol, and defining it in
this way makes it a valid command name for calling with M-x or for
binding a key to with global-set-key (see section Keymaps). If you
specify a name that has a prior definition other than another keyboard
macro, an error message is printed and nothing is changed.
Once a macro has a command name, you can save its definition in a file. Then it can be used in another editing session. First visit the file you want to save the definition in. Then use the command
M-x insert-kbd-macro RET macroname RET
This inserts some Lisp code that, when executed later, will define the same
macro with the same definition it has now. You need not understand Lisp
code to do this, because insert-kbd-macro writes the Lisp code for you.
Then save the file. The file can be loaded with load-file
(see section Libraries of Lisp Code for Emacs). If the file you save in is your init file
`~/.emacs' (see section The Init File, .emacs) then the macro will be defined each
time you run Emacs.
If you give insert-kbd-macro a prefix argument, it makes
additional Lisp code to record the keys (if any) that you have bound to the
keyboard macro, so that the macro will be reassigned the same keys when you
load the file.
Using C-x q (kbd-macro-query), you can get an effect similar
to that of query-replace, where the macro asks you each time around
whether to make a change. When you are defining the macro, type C-x
q at the point where you want the query to occur. During macro
definition, the C-x q does nothing, but when the macro is invoked the
C-x q reads a character from the terminal to decide whether to
continue.
The special answers are SPC, DEL, C-d, C-l and C-r. Any other character terminates execution of the keyboard macro and is then read as a command. SPC means to continue. DEL means to skip the remainder of this repetition of the macro, starting again from the beginning in the next repetition. C-d means to skip the remainder of this repetition and cancel further repetition. C-l redraws the screen and asks you again for a character to say what to do. C-r enters a recursive editing level, in which you can perform editing which is not part of the macro. When you exit the recursive edit using C-M-c, you are asked again how to continue with the keyboard macro. If you type a SPC at this time, the rest of the macro definition is executed. It is up to you to leave point and the text in a state such that the rest of the macro will do what you want.
C-u C-x q, which is C-x q with a numeric argument, performs a different function. It enters a recursive edit reading input from the keyboard, both when you type it during the definition of the macro, and when it is executed from the macro. During definition, the editing you do inside the recursive edit does not become part of the macro. During macro execution, the recursive edit gives you a chance to do some particularized editing. See section Recursive Editing Levels.
This section deals with the keymaps which define the bindings between keys and functions, and shows how you can customize these bindings.
A command is a Lisp function whose definition provides for interactive use. Like every Lisp function, a command has a function name, a Lisp symbol whose name usually consists of lower case letters and hyphens.
The bindings between characters and command functions are recorded in
data structures called keymaps. Emacs has many of these. One, the
global keymap, defines the meanings of the single-character keys that
are defined regardless of major mode. It is the value of the variable
global-map.
Each major mode has another keymap, its local keymap, which
contains overriding definitions for the single-character keys that are to
be redefined in that mode. Each buffer records which local keymap is
installed for it at any time, and the current buffer's local keymap is the
only one that directly affects command execution. The local keymaps for
Lisp mode, C mode, and many other major modes always exist even when not in
use. They are the values of the variables lisp-mode-map,
c-mode-map, and so on. For major modes less often used, the local
keymap is sometimes constructed only when the mode is used for the first
time in a session. This is to save space.
There are local keymaps for the minibuffer too; they contain various completion and exit commands.
minibuffer-local-map is used for ordinary input (no completion).
minibuffer-local-ns-map is similar, except that SPC exits
just like RET. This is used mainly for Mocklisp compatibility.
minibuffer-local-completion-map is for permissive completion.
minibuffer-local-must-match-map is for strict completion and
for cautious completion.
repeat-complex-command-map is for use in C-x ESC.
Finally, each prefix key has a keymap which defines the key sequences
that start with it. For example, ctl-x-map is the keymap used for
characters following a C-x.
ctl-x-map is the variable name for the map used for characters that
follow C-x.
help-map is used for characters that follow C-h.
esc-map is for characters that follow ESC. Thus, all Meta
characters are actually defined by this map.
ctl-x-4-map is for characters that follow C-x 4.
mode-specific-map is for characters that follow C-c.
The definition of a prefix key is just the keymap to use for looking up
the following character. Actually, the definition is sometimes a Lisp
symbol whose function definition is the following character keymap. The
effect is the same, but it provides a command name for the prefix key that
can be used as a description of what the prefix key is for. Thus, the
binding of C-x is the symbol Ctl-X-Prefix, whose function
definition is the keymap for C-x commands, the value of
ctl-x-map.
Prefix key definitions of this sort can appear in either the global map or a local map. The definitions of C-c, C-x, C-h and ESC as prefix keys appear in the global map, so these prefix keys are always available. Major modes can locally redefine a key as a prefix by putting a prefix key definition for it in the local map.
A mode can also put a prefix definition of a global prefix character such
as C-x into its local map. This is how major modes override the
definitions of certain keys that start with C-x. This case is
special, because the local definition does not entirely replace the global
one. When both the global and local definitions of a key are other
keymaps, the next character is looked up in both keymaps, with the local
definition overriding the global one as usual. So, the character after the
C-x is looked up in both the major mode's own keymap for redefined
C-x commands and in ctl-x-map. If the major mode's own keymap
for C-x commands contains nil, the definition from the global
keymap for C-x commands is used.
A keymap is actually a Lisp object. The simplest form of keymap is a
Lisp vector of length 128. The binding for a character in such a keymap is
found by indexing into the vector with the character as an index. A keymap
can also be a Lisp list whose car is the symbol keymap and whose
remaining elements are pairs of the form (char . binding).
Such lists are called sparse keymaps because they are used when most
of the characters' entries will be nil. Sparse keymaps are used
mainly for prefix characters.
Keymaps are only of length 128, so what about Meta characters, whose
codes are from 128 to 255? A key that contains a Meta character actually
represents it as a sequence of two characters, the first of which is
ESC. So the key M-a is really represented as ESC
a, and its binding is found at the slot for `a' in
esc-map.
The way to redefine an Emacs key is to change its entry in a keymap. You can change the global keymap, in which case the change is effective in all major modes (except those that have their own overriding local definitions for the same key). Or you can change the current buffer's local map, which affects all buffers using the same major mode.
For example,
M-x global-set-key RET C-f next-line RET
would redefine C-f to move down a line. The fact that cmd is read second makes it serve as a kind of confirmation for key.
These functions offer no way to specify a particular prefix keymap as the one to redefine in, but that is not necessary, as you can include prefixes in key. key is read by reading characters one by one until they amount to a complete key (that is, not a prefix key). Thus, if you type C-f for key, that's the end; the minibuffer is entered immediately to read cmd. But if you type C-x, another character is read; if that is 4, another character is read, and so on. For example,
M-x global-set-key RET C-x 4 $ spell-other-window RET
would redefine C-x 4 $ to run the (fictitious) command
spell-other-window.
The most general way to modify a keymap is the function define-key,
used in Lisp code (such as your `.emacs' file). define-key
takes three arguments: the keymap, the key to modify in it, and the new
definition. See section The Init File, .emacs, for an example. substitute-key-definition
is used similarly; it takes three arguments, an old definition, a new
definition and a keymap, and redefines in that keymap all keys that were
previously defined with the old definition to have the new definition
instead.
Disabling a command marks the command as requiring confirmation before it can be executed. The purpose of disabling a command is to prevent beginning users from executing it by accident and being confused.
The direct mechanism for disabling a command is to have a non-nil
disabled property on the Lisp symbol for the command. These
properties are normally set up by the user's `.emacs' file with
Lisp expressions such as
(put 'delete-region 'disabled t)
If the value of the disabled property is a string, that string
is included in the message printed when the command is used:
(put 'delete-region 'disabled
"Text deleted this way cannot be yanked back!\n")
You can make a command disabled either by editing the `.emacs' file directly or with the command M-x disable-command, which edits the `.emacs' file for you. See section The Init File, .emacs.
Attempting to invoke a disabled command interactively in Emacs causes the display of a window containing the command's name, its documentation, and some instructions on what to do immediately; then Emacs asks for input saying whether to execute the command as requested, enable it and execute, or cancel it. If you decide to enable the command, you are asked whether to do this permanently or just for the current session. Enabling permanently works by automatically editing your `.emacs' file. You can use M-x enable-command at any time to enable any command permanently.
Whether a command is disabled is independent of what key is used to invoke it; it also applies if the command is invoked using M-x. Disabling a command has no effect on calling it as a function from Lisp programs.
All the Emacs commands which parse words or balance parentheses are controlled by the syntax table. The syntax table says which characters are opening delimiters, which are parts of words, which are string quotes, and so on. Actually, each major mode has its own syntax table (though sometimes related major modes use the same one) which it installs in each buffer that uses that major mode. The syntax table installed in the current buffer is the one that all commands use, so we call it "the" syntax table. A syntax table is a Lisp object, a vector of length 256 whose elements are numbers.
The syntax table entry for a character is a number that encodes six pieces of information:
The syntactic classes are stored internally as small integers, but are usually described to or by the user with characters. For example, `(' is used to specify the syntactic class of opening delimiters. Here is a table of syntactic classes, with the characters that specify them.
The characters flagged as part of two-character comment delimiters can
have other syntactic functions most of the time. For example, `/' and
`*' in C code, when found separately, have nothing to do with
comments. The comment-delimiter significance overrides when the pair of
characters occur together in the proper order. Only the list and sexp
commands use the syntax table to find comments; the commands specifically
for comments have other variables that tell them where to find comments.
And the list and sexp commands notice comments only if
parse-sexp-ignore-comments is non-nil. This variable is set
to nil in modes where comment-terminator sequences are liable to
appear where there is no comment; for example, in Lisp mode where the
comment terminator is a newline but not every newline ends a comment.
It is possible to alter a character's syntax table entry by storing a new number in the appropriate element of the syntax table, but it would be hard to determine what number to use. Therefore, Emacs provides a command that allows you to specify the syntactic properties of a character in a convenient way.
M-x modify-syntax-entry is the command to change a character's syntax. It can be used interactively, and is also the means used by major modes to initialize their own syntax tables. Its first argument is the character to change. The second argument is a string that specifies the new syntax. When called from Lisp code, there is a third, optional argument, which specifies the syntax table in which to make the change. If not supplied, or if this command is called interactively, the third argument defaults to the current buffer's syntax table.
A description of the contents of the current syntax table can be
displayed with C-h s (describe-syntax). The description of
each character includes both the string you would have to give to
modify-syntax-entry to set up that character's current syntax, and
some English to explain that string if necessary.
When Emacs is started, it normally loads the file `.emacs' in your home directory. This file, if it exists, should contain Lisp code. It is called your init file. The command line switches `-q' and `-u' can be used to tell Emacs whether to load an init file (see section Entering and Exiting Emacs).
There can also be a default init file, which is the library named
`default.el', found via the standard search path for libraries. The
Emacs distribution contains no such library; your site may create one for
local customizations. If this library exists, it is loaded whenever you
start Emacs. But your init file, if any, is loaded first; if it sets
inhibit-default-init non-nil, then `default' is not
loaded.
If you have a large amount of code in your `.emacs' file, you
should move it into another file named `something.el',
byte-compile it (see section Libraries of Lisp Code for Emacs), and make your `.emacs'
file load the other file using load.
The `.emacs' file contains one or more Lisp function call
expressions. Each of these consists of a function name followed by
arguments, all surrounded by parentheses. For example, (setq
fill-column 60) represents a call to the function setq which is
used to set the variable fill-column (see section Filling Text) to 60.
The second argument to setq is an expression for the new value of
the variable. This can be a constant, a variable, or a function call
expression. In `.emacs', constants are used most of the time. They can be:
?x, ?\n, ?\", ?\). Note that
strings and characters are not interchangeable in Lisp; some contexts
require one and some contexts require the other.
t stands for `true'.
nil stands for `false'.
Here are some examples of doing certain commonly desired things with Lisp expressions:
(setq c-tab-always-indent nil)Here we have a variable whose value is normally
t for `true'
and the alternative is nil for `false'.
(setq-default case-fold-search nil)This sets the default value, which is effective in all buffers that do not have local values for the variable. Setting
case-fold-search
with setq affects only the current buffer's local value, which
is not what you probably want to do in an init file.
(setq default-major-mode 'text-mode)Note that
text-mode is used because it is the command for entering
the mode we want. A single-quote is written before it to make a symbol
constant; otherwise, text-mode would be treated as a variable name.
(setq text-mode-hook '(lambda () (auto-fill-mode 1)))Here we have a variable whose value should be a Lisp function. The function we supply is a list starting with
lambda, and a single
quote is written in front of it to make it (for the purpose of this
setq) a list constant rather than an expression. Lisp functions
are not explained here, but for mode hooks it is enough to know that
(auto-fill-mode 1) is an expression that will be executed when
Text mode is entered, and you could replace it with any other expression
that you like, or with several expressions in a row.
(setq text-mode-hook 'turn-on-auto-fill)This is another way to accomplish the same result.
turn-on-auto-fill is a symbol whose function definition is
(lambda () (auto-fill-mode 1)).
(load "foo")When the argument to
load is a relative pathname, not starting
with `/' or `~', load searches the directories in
load-path (see section Loading Libraries).
(load "~/foo.elc")Here an absolute file name is used, so no searching is done.
make-symbolic-link.
(global-set-key "\C-xl" 'make-symbolic-link)or
(define-key global-map "\C-xl" 'make-symbolic-link)Note once again the single-quote used to refer to the symbol
make-symbolic-link instead of its value as a variable.
(define-key c-mode-map "\C-xl" 'make-symbolic-link)
next-line in Fundamental mode
so that they run forward-line instead.
(substitute-key-definition 'next-line 'forward-line
global-map)
(global-unset-key "\C-x\C-v")One reason to undefine a key is so that you can make it a prefix. Simply defining C-x C-v anything would make C-x C-v a prefix, but C-x C-v must be freed of any non-prefix definition first.
(modify-syntax-entry ?\$ "." text-mode-syntax-table)
eval-expression without confirmation.
(put 'eval-expression 'disabled nil)
Each terminal type can have a Lisp library to be loaded into Emacs when
it is run on that type of terminal. For a terminal type named
termtype, the library is called `term/termtype' and it is
found by searching the directories load-path as usual and trying the
suffixes `.elc' and `.el'. Normally it appears in the
subdirectory `term' of the directory where most Emacs libraries are
kept.
The usual purpose of the terminal-specific library is to define the escape sequences used by the terminal's function keys using the library `keypad.el'. See the file `term/vt100.el' for an example of how this is done.
When the terminal type contains a hyphen, only the part of the name
before the first hyphen is significant in choosing the library name.
Thus, terminal types `aaa-48' and `aaa-30-rv' both use
the library `term/aaa'. The code in the library can use
(getenv "TERM") to find the full terminal type name.
The library's name is constructed by concatenating the value of the
variable term-file-prefix and the terminal type. Your `.emacs'
file can prevent the loading of the terminal-specific library by setting
term-file-prefix to nil.
The value of the variable term-setup-hook, if not nil, is
called as a function of no arguments at the end of Emacs initialization,
after both your `.emacs' file and any terminal-specific library have
been read in. You can set the value in the `.emacs' file to override
part of any of the terminal-specific libraries and to define
initializations for terminals that do not have a library.
If you type an Emacs command you did not intend, the results are often mysterious. This chapter tells what you can do to cancel your mistake or recover from a mysterious situation. Emacs bugs and system crashes are also considered.
abort-recursive-edit).
undo).
There are two ways of cancelling commands which are not finished executing: quitting with C-g, and aborting with C-] or M-x top-level. Quitting is cancelling a partially typed command or one which is already running. Aborting is getting out of a recursive editing level and cancelling the command that invoked the recursive edit.
Quitting with C-g is used for getting rid of a partially typed
command, or a numeric argument that you don't want. It also stops a
running command in the middle in a relatively safe way, so you can use it
if you accidentally give a command which takes a long time. In particular,
it is safe to quit out of killing; either your text will all still be
there, or it will all be in the kill ring (or maybe both). Quitting
an incremental search does special things documented under searching; in
general, it may take two successive C-g characters to get out of a
search. C-g works by setting the variable quit-flag to
t the instant C-g is typed; Emacs Lisp checks this variable
frequently and quits if it is non-nil. C-g is only actually
executed as a command if it is typed while Emacs is waiting for input.
If you quit twice in a row before the first C-g is recognized, you activate the "emergency escape" feature and return to the shell. See section Emergency Escape.
Aborting with C-] (abort-recursive-edit) is used to get out
of a recursive editing level and cancel the command which invoked it.
Quitting with C-g does not do this, and could not do this, because it
is used to cancel a partially typed command within the recursive
editing level. Both operations are useful. For example, if you are in the
Emacs debugger (see section The Emacs-Lisp Debugger) and have typed C-u 8 to enter a
numeric argument, you can cancel that argument with C-g and remain in
the debugger.
The command M-x top-level is equivalent to "enough" C-] commands to get you out of all the levels of recursive edits that you are in. C-] gets you out one level at a time, but M-x top-level goes out all levels at once. Both C-] and M-x top-level are like all other commands, and unlike C-g, in that they are effective only when Emacs is ready for a command. C-] is an ordinary key and has its meaning only because of its binding in the keymap. See section Recursive Editing Levels.
C-x u (undo) is not strictly speaking a way of cancelling a
command, but you can think of it as cancelling a command already finished
executing. See section Undoing Changes.
This section describes various conditions in which Emacs fails to work, and how to recognize them and correct them.
Recursive editing levels are important and useful features of Emacs, but they can seem like malfunctions to the user who does not understand them.
If the mode line has square brackets `[...]' around the parentheses that contain the names of the major and minor modes, you have entered a recursive editing level. If you did not do this on purpose, or if you don't understand what that means, you should just get out of the recursive editing level. To do so, type M-x top-level. This is called getting back to top level. See section Recursive Editing Levels.
If the data on the screen looks wrong, the first thing to do is see whether the text is really wrong. Type C-l, to redisplay the entire screen. If it appears correct after this, the problem was entirely in the previous screen update.
Display updating problems often result from an incorrect termcap entry for the terminal you are using. The file `etc/TERMS' in the Emacs distribution gives the fixes for known problems of this sort. `INSTALL' contains general advice for these problems in one of its sections. Very likely there is simply insufficient padding for certain display operations. To investigate the possibility that you have this sort of problem, try Emacs on another terminal made by a different manufacturer. If problems happen frequently on one kind of terminal but not another kind, it is likely to be a bad termcap entry, though it could also be due to a bug in Emacs that appears for terminals that have or that lack specific features.
If C-l shows that the text is wrong, try undoing the changes to it using C-x u until it gets back to a state you consider correct. Also try C-h l to find out what command you typed to produce the observed results.
If a large portion of text appears to be missing at the beginning or end of the buffer, check for the word `Narrow' in the mode line. If it appears, the text is still present, but marked off-limits. To make it visible again, type C-x w. See section Narrowing.
If Emacs spontaneously displays `I-search:' at the bottom of the screen, it means that the terminal is sending C-s and C-q according to the poorly designed xon/xoff "flow control" protocol. You should try to prevent this by putting the terminal in a mode where it will not use flow control or giving it enough padding that it will never send a C-s. If that cannot be done, you must tell Emacs to expect flow control to be used, until you can get a properly designed terminal.
Information on how to do these things can be found in the file `INSTALL' in the Emacs distribution.
Because at times there have been bugs causing Emacs to loop without
checking quit-flag, a special feature causes Emacs to be suspended
immediately if you type a second C-g while the flag is already set,
so you can always get out of GNU Emacs. Normally Emacs recognizes and
clears quit-flag (and quits!) quickly enough to prevent this from
happening.
When you resume Emacs after a suspension caused by multiple C-g, it asks two questions before going back to what it had been doing:
Auto-save? (y or n) Abort (and dump core)? (y or n)
Answer each one with y or n followed by RET.
Saying y to `Auto-save?' causes immediate auto-saving of all modified buffers in which auto-saving is enabled.
Saying y to `Abort (and dump core)?' causes an illegal instruction to be
executed, dumping core. This is to enable a wizard to figure out why Emacs
was failing to quit in the first place. Execution does not continue
after a core dump. If you answer n, execution does continue. With
luck, GNU Emacs will ultimately check quit-flag and quit normally.
If not, and you type another C-g, it is suspended again.
If Emacs is not really hung, just slow, you may invoke the double C-g feature without really meaning to. Then just resume and answer n to both questions, and you will arrive at your former state. Presumably the quit you requested will happen soon.
The double-C-g feature may be turned off when Emacs is running under a window system, since the window system always enables you to kill Emacs or to create another window and run another program.
If using Emacs (or something else) becomes terribly frustrating and none of the techniques described above solve the problem, Emacs can still help you.
First, if the Emacs you are using is not responding to commands, type C-g C-g to get out of it and then start a new one.
The doctor will make you feel better. Each time you say something to the doctor, you must end it by typing RET RET. This lets the doctor know you are finished.
Sometimes you will encounter a bug in Emacs. Although we cannot promise we can or will fix the bug, and we might not even agree that it is a bug, we want to hear about bugs you encounter in case we do want to fix them.
To make it possible for us to fix a bug, you must report it. In order to do so effectively, you must know when and how to do it.
If Emacs executes an illegal instruction, or dies with an operating system error message that indicates a problem in the program (as opposed to something like "disk full"), then it is certainly a bug.
If Emacs updates the display in a way that does not correspond to what is in the buffer, then it is certainly a bug. If a command seems to do the wrong thing but the problem corrects itself if you type C-l, it is a case of incorrect display updating.
Taking forever to complete a command can be a bug, but you must make certain that it was really Emacs's fault. Some commands simply take a long time. Type C-g and then C-h l to see whether the input Emacs received was what you intended to type; if the input was such that you know it should have been processed quickly, report a bug. If you don't know whether the command should take a long time, find out by looking in the manual or by asking for assistance.
If a command you are familiar with causes an Emacs error message in a case where its usual definition ought to be reasonable, it is probably a bug.
If a command does the wrong thing, that is a bug. But be sure you know for certain what it ought to have done. If you aren't familiar with the command, or don't know for certain how the command is supposed to work, then it might actually be working right. Rather than jumping to conclusions, show the problem to someone who knows for certain.
Finally, a command's intended definition may not be best for editing with. This is a very important sort of problem, but it is also a matter of judgment. Also, it is easy to come to such a conclusion out of ignorance of some of the existing features. It is probably best not to complain about such a problem until you have checked the documentation in the usual ways, feel confident that you understand it, and know for certain that what you want is not available. If you are not sure what the command is supposed to do after a careful reading of the manual, check the index and glossary for any terms that may be unclear. If you still do not understand, this indicates a bug in the manual. The manual's job is to make everything clear. It is just as important to report documentation bugs as program bugs.
If the on-line documentation string of a function or variable disagrees with the manual, one of them must be wrong, so report the bug.
When you decide that there is a bug, it is important to report it and to report it in a way which is useful. What is most useful is an exact description of what commands you type, starting with the shell command to run Emacs, until the problem happens. Always include the version number of Emacs that you are using; type M-x emacs-version to print this.
The most important principle in reporting a bug is to report facts, not hypotheses or categorizations. It is always easier to report the facts, but people seem to prefer to strain to posit explanations and report them instead. If the explanations are based on guesses about how Emacs is implemented, they will be useless; we will have to try to figure out what the facts must have been to lead to such speculations. Sometimes this is impossible. But in any case, it is unnecessary work for us.
For example, suppose that you type C-x C-f /glorp/baz.ugh RET, visiting a file which (you know) happens to be rather large, and Emacs prints out `I feel pretty today'. The best way to report the bug is with a sentence like the preceding one, because it gives all the facts and nothing but the facts.
Do not assume that the problem is due to the size of the file and say, "When I visit a large file, Emacs prints out `I feel pretty today'." This is what we mean by "guessing explanations". The problem is just as likely to be due to the fact that there is a `z' in the file name. If this is so, then when we got your report, we would try out the problem with some "large file", probably with no `z' in its name, and not find anything wrong. There is no way in the world that we could guess that we should try visiting a file with a `z' in its name.
Alternatively, the problem might be due to the fact that the file starts with exactly 25 spaces. For this reason, you should make sure that you inform us of the exact contents of any file that is needed to reproduce the bug. What if the problem only occurs when you have typed the C-x C-a command previously? This is why we ask you to give the exact sequence of characters you typed since starting to use Emacs.
You should not even say "visit a file" instead of C-x C-f unless you know that it makes no difference which visiting command is used. Similarly, rather than saying "if I have three characters on the line," say "after I type RET A B C RET C-p," if that is the way you entered the text.
If you are not in Fundamental mode when the problem occurs, you should say what mode you are in.
If the manifestation of the bug is an Emacs error message, it is
important to report not just the text of the error message but a backtrace
showing how the Lisp program in Emacs arrived at the error. To make the
backtrace, you must execute the Lisp expression
(setq debug-on-error t) before the error happens (that is to
say, you must execute that expression and then make the bug happen). This
causes the Lisp debugger to run (see section The Emacs-Lisp Debugger). The debugger's
backtrace can be copied as text into the bug report. This use of the
debugger is possible only if you know how to make the bug happen again. Do
note the error message the first time the bug happens, so if you can't make
it happen again, you can report at least that.
Check whether any programs you have loaded into the Lisp world, including
your `.emacs' file, set any variables that may affect the functioning
of Emacs. Also, see whether the problem happens in a freshly started Emacs
without loading your `.emacs' file (start Emacs with the -q switch
to prevent loading the init file.) If the problem does not occur
then, it is essential that we know the contents of any programs that you
must load into the Lisp world in order to cause the problem to occur.
If the problem does depend on an init file or other Lisp programs that are not part of the standard Emacs system, then you should make sure it is not a bug in those programs by complaining to their maintainers first. After they verify that they are using Emacs in a way that is supposed to work, they should report the bug.
If you can tell us a way to cause the problem without visiting any files, please do so. This makes it much easier to debug. If you do need files, make sure you arrange for us to see their exact contents. For example, it can often matter whether there are spaces at the ends of lines, or a newline after the last line in the buffer (nothing ought to care whether the last line is terminated, but tell that to the bugs).
The easy way to record the input to Emacs precisely is to to write a dribble file; execute the Lisp expression
(open-dribble-file "~/dribble")
using Meta-ESC or from the `*scratch*' buffer just after starting Emacs. From then on, all Emacs input will be written in the specified dribble file until the Emacs process is killed.
For possible display bugs, it is important to report the terminal type
(the value of environment variable TERM), the complete termcap entry
for the terminal from `/etc/termcap' (since that file is not identical
on all machines), and the output that Emacs actually sent to the terminal.
The way to collect this output is to execute the Lisp expression
(open-termscript "~/termscript")
using Meta-ESC or from the `*scratch*' buffer just after starting Emacs. From then on, all output from Emacs to the terminal will be written in the specified termscript file as well, until the Emacs process is killed. If the problem happens when Emacs starts up, put this expression into your `.emacs' file so that the termscript file will be open when Emacs displays the screen for the first time. Be warned: it is often difficult, and sometimes impossible, to fix a terminal-dependent bug without access to a terminal of the type that stimulates the bug.
The address for reporting bugs is
GNU Emacs Bugs 545 Tech Sq, rm 703 Cambridge, MA 02139
or send email to `mit-eddie!bug-gnu-emacs' (Usenet) or `bug-gnu-emacs@prep.ai.mit.edu' (Internet).
Once again, we do not promise to fix the bug; but if the bug is serious, or ugly, or easy to fix, chances are we will want to.
For those of you who are downgrading from version 18 to version 17 of GNU Emacs, here is a list of the old features. You will note many simplifications; complicated features have been eliminated. The list does not include changes affecting only topics not dealt with in this manual.
search-low-speed and search-slow-window-lines
have been renamed to start with isearch instead of search.
outline-regexp has also been eliminated in version
17.
c-tab-always-indent has been eliminated and Emacs acts as if
it were t. See section Customizing C Indentation.
load-file and load-library are replaced
with one command, load. This command is logically the same as
version 18 load-library, but due to changes in the order of
searching it can also serve in place of load-file.
See section Loading Libraries.
The search order in version 17 is:
nil, meaning
the current default directory.
As a result, the first file name that load tries is the one
load-file would use in version 18: no suffix, and current
default directory.
setq-default has been eliminated. Use
set-default and quote the variable name, as in
(set-default 'variable value)Several built-in variables now are always local to all buffers. These variables are
tab-width, ctl-arrow,
truncate-lines, fill-column, left-margin,
mode-line-format, abbrev-mode, overwrite-mode,
case-fold-search, auto-fill-hook,
selective-display.
set-default does not work with these variables. They do have
defaults, but the defaults affect only buffers yet to be created. The
only way to set the default for variable foo is to set the
variable named default-foo, such as
default-case-fold-search and default-fill-column.
nil.
backup-by-copying-when-mismatch
find-file-hooks
find-file-not-found-hooks
write-file-hooks
file-precious-flag
no-redraw-on-reenter
GNU, which stands for Gnu's Not Unix, is the name for the complete Unix-compatible software system which I am writing so that I can give it away free to everyone who can use it. Several other volunteers are helping me. Contributions of time, money, programs and equipment are greatly needed.
So far we have an Emacs text editor with Lisp for writing editor commands, a source level debugger, a yacc-compatible parser generator, a linker, and around 35 utilities. A shell (command interpreter) is nearly completed. A new portable optimizing C compiler has compiled itself and may be released this year. An initial kernel exists but many more features are needed to emulate Unix. When the kernel and compiler are finished, it will be possible to distribute a GNU system suitable for program development. We will use TeX as our text formatter, but an nroff is being worked on. We will use the free, portable X window system as well. After this we will add a portable Common Lisp, an Empire game, a spreadsheet, and hundreds of other things, plus on-line documentation. We hope to supply, eventually, everything useful that normally comes with a Unix system, and more.
GNU will be able to run Unix programs, but will not be identical to Unix. We will make all improvements that are convenient, based on our experience with other operating systems. In particular, we plan to have longer filenames, file version numbers, a crashproof file system, filename completion perhaps, terminal-independent display support, and perhaps eventually a Lisp-based window system through which several Lisp programs and ordinary Unix programs can share a screen. Both C and Lisp will be available as system programming languages. We will try to support UUCP, MIT Chaosnet, and Internet protocols for communication.
GNU is aimed initially at machines in the 68000/16000 class with virtual memory, because they are the easiest machines to make it run on. The extra effort to make it run on smaller machines will be left to someone who wants to use it on them.
To avoid horrible confusion, please pronounce the `G' in the word `GNU' when it is the name of this project.
I consider that the golden rule requires that if I like a program I must share it with other people who like it. Software sellers want to divide the users and conquer them, making each user agree not to share with others. I refuse to break solidarity with other users in this way. I cannot in good conscience sign a nondisclosure agreement or a software license agreement. For years I worked within the Artificial Intelligence Lab to resist such tendencies and other inhospitalities, but eventually they had gone too far: I could not remain in an institution where such things are done for me against my will.
So that I can continue to use computers without dishonor, I have decided to put together a sufficient body of free software so that I will be able to get along without any software that is not free. I have resigned from the AI lab to deny MIT any legal excuse to prevent me from giving GNU away.
Unix is not my ideal system, but it is not too bad. The essential features of Unix seem to be good ones, and I think I can fill in what Unix lacks without spoiling them. And a system compatible with Unix would be convenient for many other people to adopt.
GNU is not in the public domain. Everyone will be permitted to modify and redistribute GNU, but no distributor will be allowed to restrict its further redistribution. That is to say, proprietary modifications will not be allowed. I want to make sure that all versions of GNU remain free.
I have found many other programmers who are excited about GNU and want to help.
Many programmers are unhappy about the commercialization of system software. It may enable them to make more money, but it requires them to feel in conflict with other programmers in general rather than feel as comrades. The fundamental act of friendship among programmers is the sharing of programs; marketing arrangements now typically used essentially forbid programmers to treat others as friends. The purchaser of software must choose between friendship and obeying the law. Naturally, many decide that friendship is more important. But those who believe in law often do not feel at ease with either choice. They become cynical and think that programming is just a way of making money.
By working on and using GNU rather than proprietary programs, we can be hospitable to everyone and obey the law. In addition, GNU serves as an example to inspire and a banner to rally others to join us in sharing. This can give us a feeling of harmony which is impossible if we use software that is not free. For about half the programmers I talk to, this is an important happiness that money cannot replace.
I am asking computer manufacturers for donations of machines and money. I'm asking individuals for donations of programs and work.
One consequence you can expect if you donate machines is that GNU will run on them at an early date. The machines should be complete, ready to use systems, approved for use in a residential area, and not in need of sophisticated cooling or power.
I have found very many programmers eager to contribute part-time work for GNU. For most projects, such part-time distributed work would be very hard to coordinate; the independently-written parts would not work together. But for the particular task of replacing Unix, this problem is absent. A complete Unix system contains hundreds of utility programs, each of which is documented separately. Most interface specifications are fixed by Unix compatibility. If each contributor can write a compatible replacement for a single Unix utility, and make it work properly in place of the original on a Unix system, then these utilities will work right when put together. Even allowing for Murphy to create a few unexpected problems, assembling these components will be a feasible task. (The kernel will require closer communication and will be worked on by a small, tight group.)
If I get donations of money, I may be able to hire a few people full or part time. The salary won't be high by programmers' standards, but I'm looking for people for whom building community spirit is as important as making money. I view this as a way of enabling dedicated people to devote their full energies to working on GNU by sparing them the need to make a living in another way.
Once GNU is written, everyone will be able to obtain good system software free, just like air.
This means much more than just saving everyone the price of a Unix license. It means that much wasteful duplication of system programming effort will be avoided. This effort can go instead into advancing the state of the art.
Complete system sources will be available to everyone. As a result, a user who needs changes in the system will always be free to make them himself, or hire any available programmer or company to make them for him. Users will no longer be at the mercy of one programmer or company which owns the sources and is in sole position to make changes.
Schools will be able to provide a much more educational environment by encouraging all students to study and improve the system code. Harvard's computer lab used to have the policy that no program could be installed on the system if its sources were not on public display, and upheld it by actually refusing to install certain programs. I was very much inspired by this.
Finally, the overhead of considering who owns the system software and what one is or is not entitled to do with it will be lifted.
Arrangements to make people pay for using a program, including licensing of copies, always incur a tremendous cost to society through the cumbersome mechanisms necessary to figure out how much (that is, which programs) a person must pay for. And only a police state can force everyone to obey them. Consider a space station where air must be manufactured at great cost: charging each breather per liter of air may be fair, but wearing the metered gas mask all day and all night is intolerable even if everyone can afford to pay the air bill. And the TV cameras everywhere to see if you ever take the mask off are outrageous. It's better to support the air plant with a head tax and chuck the masks.
Copying all or parts of a program is as natural to a programmer as breathing, and as productive. It ought to be as free.
"Nobody will use it if it is free, because that means they can't rely on any support."
"You have to charge for the program to pay for providing the support."
If people would rather pay for GNU plus service than get GNU free without service, a company to provide just service to people who have obtained GNU free ought to be profitable.
We must distinguish between support in the form of real programming work and mere handholding. The former is something one cannot rely on from a software vendor. If your problem is not shared by enough people, the vendor will tell you to get lost.
If your business needs to be able to rely on support, the only way is to have all the necessary sources and tools. Then you can hire any available person to fix your problem; you are not at the mercy of any individual. With Unix, the price of sources puts this out of consideration for most businesses. With GNU this will be easy. It is still possible for there to be no available competent person, but this problem cannot be blamed on distibution arrangements. GNU does not eliminate all the world's problems, only some of them.
Meanwhile, the users who know nothing about computers need handholding: doing things for them which they could easily do themselves but don't know how.
Such services could be provided by companies that sell just hand-holding and repair service. If it is true that users would rather spend money and get a product with service, they will also be willing to buy the service having got the product free. The service companies will compete in quality and price; users will not be tied to any particular one. Meanwhile, those of us who don't need the service should be able to use the program without paying for the service.
"You cannot reach many people without advertising, and you must charge for the program to support that."
"It's no use advertising a program people can get free."
There are various forms of free or very cheap publicity that can be used to inform numbers of computer users about something like GNU. But it may be true that one can reach more microcomputer users with advertising. If this is really so, a business which advertises the service of copying and mailing GNU for a fee ought to be successful enough to pay for its advertising and more. This way, only the users who benefit from the advertising pay for it.
On the other hand, if many people get GNU from their friends, and such companies don't succeed, this will show that advertising was not really necessary to spread GNU. Why is it that free market advocates don't want to let the free market decide this?
"My company needs a proprietary operating system to get a competitive edge."
GNU will remove operating system software from the realm of competition. You will not be able to get an edge in this area, but neither will your competitors be able to get an edge over you. You and they will compete in other areas, while benefitting mutually in this one. If your business is selling an operating system, you will not like GNU, but that's tough on you. If your business is something else, GNU can save you from being pushed into the expensive business of selling operating systems.
I would like to see GNU development supported by gifts from many manufacturers and users, reducing the cost to each.
"Don't programmers deserve a reward for their creativity?"
If anything deserves a reward, it is social contribution. Creativity can be a social contribution, but only in so far as society is free to use the results. If programmers deserve to be rewarded for creating innovative programs, by the same token they deserve to be punished if they restrict the use of these programs.
"Shouldn't a programmer be able to ask for a reward for his creativity?"
There is nothing wrong with wanting pay for work, or seeking to maximize one's income, as long as one does not use means that are destructive. But the means customary in the field of software today are based on destruction.
Extracting money from users of a program by restricting their use of it is destructive because the restrictions reduce the amount and the ways that the program can be used. This reduces the amount of wealth that humanity derives from the program. When there is a deliberate choice to restrict, the harmful consequences are deliberate destruction.
The reason a good citizen does not use such destructive means to become wealthier is that, if everyone did so, we would all become poorer from the mutual destructiveness. This is Kantian ethics; or, the Golden Rule. Since I do not like the consequences that result if everyone hoards information, I am required to consider it wrong for one to do so. Specifically, the desire to be rewarded for one's creativity does not justify depriving the world in general of all or part of that creativity.
"Won't programmers starve?"
I could answer that nobody is forced to be a programmer. Most of us cannot manage to get any money for standing on the street and making faces. But we are not, as a result, condemned to spend our lives standing on the street making faces, and starving. We do something else.
But that is the wrong answer because it accepts the questioner's implicit assumption: that without ownership of software, programmers cannot possibly be paid a cent. Supposedly it is all or nothing.
The real reason programmers will not starve is that it will still be possible for them to get paid for programming; just not paid as much as now.
Restricting copying is not the only basis for business in software. It is the most common basis because it brings in the most money. If it were prohibited, or rejected by the customer, software business would move to other bases of organization which are now used less often. There are always numerous ways to organize any kind of business.
Probably programming will not be as lucrative on the new basis as it is now. But that is not an argument against the change. It is not considered an injustice that sales clerks make the salaries that they now do. If programmers made the same, that would not be an injustice either. (In practice they would still make considerably more than that.)
"Don't people have a right to control how their creativity is used?"
"Control over the use of one's ideas" really constitutes control over other people's lives; and it is usually used to make their lives more difficult.
People who have studied the issue of intellectual property rights carefully (such as lawyers) say that there is no intrinsic right to intellectual property. The kinds of supposed intellectual property rights that the government recognizes were created by specific acts of legislation for specific purposes.
For example, the patent system was established to encourage inventors to disclose the details of their inventions. Its purpose was to help society rather than to help inventors. At the time, the life span of 17 years for a patent was short compared with the rate of advance of the state of the art. Since patents are an issue only among manufacturers, for whom the cost and effort of a license agreement are small compared with setting up production, the patents often do not do much harm. They do not obstruct most individuals who use patented products.
The idea of copyright did not exist in ancient times, when authors frequently copied other authors at length in works of non-fiction. This practice was useful, and is the only way many authors' works have survived even in part. The copyright system was created expressly for the purpose of encouraging authorship. In the domain for which it was invented--books, which could be copied economically only on a printing press--it did little harm, and did not obstruct most of the individuals who read the books.
All intellectual property rights are just licenses granted by society because it was thought, rightly or wrongly, that society as a whole would benefit by granting them. But in any particular situation, we have to ask: are we really better off granting such license? What kind of act are we licensing a person to do?
The case of programs today is very different from that of books a hundred years ago. The fact that the easiest way to copy a program is from one neighbor to another, the fact that a program has both source code and object code which are distinct, and the fact that a program is used rather than read and enjoyed, combine to create a situation in which a person who enforces a copyright is harming society as a whole both materially and spiritually; in which a person should not do so regardless of whether the law enables him to.
"Competition makes things get done better."
The paradigm of competition is a race: by rewarding the winner, we encourage everyone to run faster. When capitalism really works this way, it does a good job; but its defenders are wrong in assuming it always works this way. If the runners forget why the reward is offered and become intent on winning, no matter how, they may find other strategies--such as, attacking other runners. If the runners get into a fist fight, they will all finish late.
Proprietary and secret software is the moral equivalent of runners in a fist fight. Sad to say, the only referee we've got does not seem to object to fights; he just regulates them ("For every ten yards you run, you can fire one shot"). He really ought to break them up, and penalize runners for even trying to fight.
"Won't everyone stop programming without a monetary incentive?"
Actually, many people will program with absolutely no monetary incentive. Programming has an irresistible fascination for some people, usually the people who are best at it. There is no shortage of professional musicians who keep at it even though they have no hope of making a living that way.
But really this question, though commonly asked, is not appropriate to the situation. Pay for programmers will not disappear, only become less. So the right question is, will anyone program with a reduced monetary incentive? My experience shows that they will.
For more than ten years, many of the world's best programmers worked at the Artificial Intelligence Lab for far less money than they could have had anywhere else. They got many kinds of non-monetary rewards: fame and appreciation, for example. And creativity is also fun, a reward in itself.
Then most of them left when offered a chance to do the same interesting work for a lot of money.
What the facts show is that people will program for reasons other than riches; but if given a chance to make a lot of money as well, they will come to expect and demand it. Low-paying organizations do poorly in competition with high-paying ones, but they do not have to do badly if the high-paying ones are banned.
"We need the programmers desperately. If they demand that we stop helping our neighbors, we have to obey."
You're never so desperate that you have to obey this sort of demand. Remember: millions for defense, but not a cent for tribute!
"Programmers need to make a living somehow."
In the short run, this is true. However, there are plenty of ways that programmers could make a living without selling the right to use a program. This way is customary now because it brings programmers and businessmen the most money, not because it is the only way to make a living. It is easy to find other ways if you want to find them. Here are a number of examples.
A manufacturer introducing a new computer will pay for the porting of operating systems onto the new hardware.
The sale of teaching, hand-holding and maintenance services could also employ programmers.
People with new ideas could distribute programs as freeware, asking for donations from satisfied users, or selling hand-holding services. I have met people who are already working this way successfully.
Users with related needs can form users' groups, and pay dues. A group would contract with programming companies to write programs that the group's members would like to use.
All sorts of development can be funded with a Software Tax:
Suppose everyone who buys a computer has to pay x percent of the price as a software tax. The government gives this to an agency like the NSF to spend on software development.
But if the computer buyer makes a donation to software development himself, he can take a credit against the tax. He can donate to the project of his own choosing--often, chosen because he hopes to use the results when it is done. He can take a credit for any amount of donation up to the total tax he had to pay.
The total tax rate could be decided by a vote of the payers of the tax, weighted according to the amount they will be taxed on.
The consequences:
- The computer-using community supports software development.
- This community decides what level of support is needed.
- Users who care which projects their share is spent on can choose this for themselves.
In the long run, making programs free is a step toward the post-scarcity world, where nobody will have to work very hard just to make a living. People will be free to devote themselves to activities that are fun, such as programming, after spending the necessary ten hours a week on required tasks such as legislation, family counseling, robot repair and asteroid prospecting. There will be no need to be able to make a living from programming.
We have already greatly reduced the amount of work that the whole society must do for its actual productivity, but only a little of this has translated itself into leisure for workers because much nonproductive activity is required to accompany productive activity. The main causes of this are bureaucracy and isometric struggles against competition. Free software will greatly reduce these drains in the area of software production. We must do this, in order for technical gains in productivity to translate into less work for us.
defun. See section Defuns.
next-line.
See section Keymaps.