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tar Operations(This message will disappear, once this node revised.)
This chapter describes the basic operations supported by the tar
program. A given invocation of tar will do exactly one of these
operations.
An archive member in normally extracted into a file with the same name
as the archive member. However, you can use the `--to-stdout' (`-O') to
cause tar to write extracted archive members to standard output.
If you extract multiple members, they appear on standard output
concatenated, in the order they are found in the archive.
The `--create' (`-c') operation writes a new archive, and the
`--extract' (`-x') operation reads files from an archive and writes them
into the file system. You can use other tar operations to
write new information into an existing archive (adding files to it,
adding another archive to it, or deleting files from it), and you can
read a list of the files in an archive without extracting it using the
`--list' (`-t') operation.
The primary argument to tar is the operation, which specifies
what tar does. tar can be used to:
FIXME: xref Reading and Writing, for more information about these operations.
Option arguments to tar change details of the operation, such as
archive format, archive name, or level of user interaction. You can
specify more than one option. All options are optional.
File Name arguments specify which files (including directory files) to archive, extract, delete or otherwise operate on.
If you don't use any file name arguments, `--append' (`-r'), `--update' (`-u') and
`--delete' will do nothing. The other operations of tar will act on
defaults.
When you use a file name argument to specify a directory file, tar
acts on all the files in that directory, including sub-directories.
You must give exactly one option from the following list to tar. This
option specifies the basic operation for tar to perform.
The remaining options to tar change details of the operation,
such as archive format, archive name, or level of user interaction.
You can specify more than one option.
The remaining arguments are interpreted either as file names or as
member names, depending on the basic operation tar is
performing. For `--append' (`-r') and `--create' (`-c') these arguments
specify the names of files (which must already exist) to place in the
archive. For the remaining operation types, the additional arguments
specify archive members to compare, delete, extract, list, or update.
When naming archive members, you must give the exact name of the member
in the archive, as it is printed by `--list' (`-t'). When naming
files, the normal file name rules apply.
If you don't use any additional arguments, `--append' (`-r'),
`--concatenate' (`-A'), and `--delete' will do nothing. Naturally,
`--create' (`-c') will make an empty archive if given no files to add.
The other operations of tar (`--list' (`-t'), `--extract' (`-x'),
`--compare' (`-d'), and `--update' (`-u')) will act on the entire contents
of the archive.
If you give the name of a directory as either a file name or a member
name, then tar acts recursively on all the files and directories
beneath that directory. For example, the name `/' identifies all
the files in the filesystem to tar.
The operation argument to tar specifies which action you want to
take.
tar program to the standard
error.
The program tar can create an archive, extract files from an
archive, modify an archive, or list an archive's contents. Each time
you run tar, you must give a command to specify which one
of these things you want to do.
The command must always be in the first argument to tar.
This argument can also contain options (
FIXME: pxref Invoking tar). For compatibility with Unix
tar, the first argument is
always treated as containing command and option letters even if it
doesn't start with `-'. Thus, `tar c' is equivalent to
`tar -c': both of them specify the `--create' (`-c') command
to create an archive.
In addition, a set of long-named options are provided which can be used instead of or intermixed with the single-letter flags. The long-named options are meant to be easy to remember and logical, while the single letter flags may not always be. Long-named options begin with `--'.
Arguments after the first are either options, if they start with `-' or `--', or files to operate on.
The file names that you give as arguments are the files that tar
will act on--for example, they are the files to put in the archive, or
the files to extract from it. If you don't give any file name
arguments, the default depends on which command you used. Some commands
use all relevant files; some commands have no default and will report an
error if you don't specify files.
If a file name argument actually names a directory, then that directory and all files and subdirectories (recursively) in it are used.
Here is a list of the tar commands:
-c
--create
This command tells tar to create a new archive that contains
the file(s) specified on the command line. If you don't specify
files, all the files in the current directory are used.
If the archive file already exists, it is overwritten; the old contents are lost.
-x
--extract
--get
This command causes tar to extract the specified files from
the archive. If no file names are given, all the files in the archive
will be extracted.
-t
--list
This command causes tar to display a list of the files in
the archive. If you specify file names, only the files that you
specify will be mentioned (but each of them is mentioned only if it
appears in the archive).
-d
--diff
--compare
This command causes tar to compare the archive with the files
in the file system. It will report differences in file size, mode,
owner, and contents. If a file exists in the archive, but not in
the file system, tar will report this.
If you specify file names, those files are compared with the tape and they must all exist in the archive. If you don't specify files, all the files in the archive are compared.
-r
--append
This command causes tar to add the specified file(s) to the end
of the archive. This assumes that the archive file already exists
and is in the proper format (which probably means it was created
previously with the tar program). If the archive is not in a
format that tar understands, the results will be unpredictable.
You must specify the files to be used; there is no default.
-u
--update
This command causes tar to add the specified files to the end
of the archive, like `--append' (`-r'), but only when a file doesn't
already exist in the archive or is newer than the version in the
archive (the last-modification time is compared). Adding files to
the end of an archive can be very slow.
You must specify the files to be used; there is no default.
-A
--catenate
--concatenate
This command is used for concatenating several archive files into one
big archive file. The files to operate on should all be archive files.
They are all appended to the end of the archive file which tar
works on. (The other files are not changed).
You might be tempted to use cat for this, but it won't ordinarily
work. A tar archive contains data which indicates the end of the
archive, so appended material is ignored. This command works because it
removes the end-of-archive markers from the middle of the result.
--delete
This command causes tar to delete the specified files from the
archive. This command is extremely slow. Warning: Use of this command
on archives stored on magnetic tape may result in a scrambled archive.
There is no safe way (except for completely re-writing the archive)
to delete files from a magnetic tape.
The program tar can create an archive, extract files from an
archive, modify an archive, or list an archive's contents. Each time
you run tar, you must give a command to specify which one
of these things you want to do.
The command must always be in the first argument to tar.
This argument can also contain options (
FIXME: pxref Invoking tar). For compatibility with Unix
tar, the first argument is
always treated as containing command and option letters even if it
doesn't start with `-'. Thus, `tar c' is equivalent to
`tar -c': both of them specify the `--create' (`-c') command
to create an archive.
In addition, a set of long-named options are provided which can be used instead of or intermixed with the single-letter flags. The long-named options are meant to be easy to remember and logical, while the single letter flags may not always be. Long-named options begin with `--'.
Arguments after the first are either options, if they start with `-' or `--', or files to operate on.
The file names that you give as arguments are the files that tar
will act on--for example, they are the files to put in the archive, or
the files to extract from it. If you don't give any file name
arguments, the default depends on which command you used. Some commands
use all relevant files; some commands have no default and will report an
error if you don't specify files.
If a file name argument actually names a directory, then that directory and all files and subdirectories (recursively) in it are used.
Once an archive is created, you can add new archive members to it, add the contents of another archive, add newer versions of members already stored, or delete archive members already stored.
To find out what files are already stored in an archive, use `tar --list --file=archive-name'.
FIXME: xref Listing Contents.
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