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The Structure of an Archive

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While an archive may contain many files, the archive itself is a single ordinary file. Like any other file, an archive file can be written to a storage device such as a tape or disk, sent through a pipe or over a network, saved on the active file system, or even stored in another archive. An archive file is not easy to read or manipulate without using the tar utility or Tar mode in Emacs.

Physically, an archive consists of a series of file entries terminated by an end-of-archive entry, which consists of 512 zero bytes. A file entry usually describes one of the files in the archive (an archive member), and consists of a file header and the contents of the file. File headers contain file names and statistics, checksum information which tar uses to detect file corruption, and information about file types.

More than archive member can have the same file name. One way this situation can occur is if more than one version of a file has been stored in the archive. For information about adding new versions of a file to an archive,

FIXME: pxref Modifying

In addition to entries describing archive members, an archive may contain entries which tar itself uses to store information.

FIXME: xref Archive Label
, for an example of such an archive entry.

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