(tar)Modifiers Options

Archive Structure

Format Control

Operation mode modifiers
========================

     *(This message will disappear, once this node revised.)*

   Operation mode modifiers

`-W'
`--verify'
     Attempt to verify the archive after writing.

     This option causes `tar' to verify the archive after writing it.
     Each volume is checked after it is written, and any discrepancies
     are recorded on the standard error output.

     Verification requires that the archive be on a back-space-able
     medium.  This means pipes, some cartridge tape drives, and some
     other devices cannot be verified.

`--remove-files'
     Remove files after adding them to the archive.

`-k'
`--keep-old-files'
     Do not overwrite existing files from archive.

     The `--keep-old-files' (`-k') option prevents `tar' from
     over-writing existing files with files with the same name from the
     archive.

     The `--keep-old-files' (`-k') option is meaningless with `--list'
     (`-t').

`-S'
`--sparse'
     Handle sparse files efficiently.

     This option causes all files to be put in the archive to be tested
     for sparseness, and handled specially if they are.  The `--sparse'
     (`-S') option is useful when many `dbm' files, for example, are
     being backed up.  Using this option dramatically decreases the
     amount of space needed to store such a file.

     In later versions, this option may be removed, and the testing and
     treatment of sparse files may be done automatically with any
     special GNU options.  For now, it is an option needing to be
     specified on the command line with the creation or updating of an
     archive.

`-O'
`--to-stdout'
     Extract files to standard output.

     When this option is used, instead of creating the files specified,
     `tar' writes the contents of the files extracted to its standard
     output.  This may be useful if you are only extracting the files in
     order to send them through a pipe.

     This option is meaningless with `--list' (`-t').

`--ignore-failed-read'
     Do not exit with non-zero on unreadable files.

FIXME: This section needs to be written

   *To come:* using Unix file linking capability to recreate directory
structures--linking files into one subdirectory and then `tar'ring that
directory.

   *to come:* nice hairy example using absolute-names, newer, etc.

   Piping one `tar' to another is an easy way to copy a directory's
contents from one disk to another, while preserving the dates, modes,
owners and link-structure of all the files therein.

     cd sourcedirectory; tar cf - . | (cd targetdir; tar xf -)

or

FIXME: the following using standard input/output correct??

     cd sourcedirectory; tar --create --file=- . | (cd targetdir; tar --extract --file=-)

Archive files can be used for transporting a group of files from one
system to another:  put all relevant files into an archive on one
computer system, transfer the archive to another, and extract the
contents there. The basic transfer medium might be magnetic tape,
Internet FTP, or even electronic mail (though you must encode the
archive with `uuencode' in order to transport it properly by mail).
Both machines do not have to use the same operating system, as long as
they both support the `tar' program.
FIXME: mention uuencode on a paragraph of its own

FIXME: end construction