(tar)Type Options

Compression

Attributes Options

Format Control

Archive format selection
========================

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   Archive format selection

`-V NAME'
`--label=NAME'
     Create archive with volume name NAME.

     This option causes `tar' to write out a "volume header" at the
     beginning of the archive.  If `--multi-volume' (`-M') is used, each
     volume of the archive will have a volume header of `NAME Volume
     N', where N is 1 for the first volume, 2 for the next, and so on.

`-z'
`--gzip'
`--ungzip'
     Filter the archive through `gzip'.

     This option works on physical devices (tape drives, etc.) and
     remote files as well as on normal files; data to or from such
     devices or remote files is reblocked by another copy of the `tar'
     program to enforce the specified (or default) block size.  The
     default compression parameters are used; if you need to override
     them, avoid the `--gzip' (`-z') option and run `gzip' explicitly.
     (Or set the `GZIP' environment variable.)

     If the `--gzip' (`-z') option is given twice, or the
     `--compress-blocks' option is used, `tar' will pad the archive out
     to the next block boundary (
     FIXME: pxref Blocking
     ).  This may be useful with some devices that require that all
     write operations be a multiple of a certain size.

     The `--gzip' (`-z') option does not work with the `--multi-volume'
     (`-M') option, or with the `--update' (`-u'), `--append' (`-r'),
     `--concatenate' (`-A'), or `--delete' commands.

     It is not exact to say that GNU `tar' is to work in concert with
     `gzip' in a way similar to `zip', say.  Surely, it is possible
     that `tar' and `gzip' be done with a single call, like in:

          tar cfz archive.tar.gz subdir

     to save all of `subdir' into a `gzip''ed archive.  Later you can
     do:

          tar xfz archive.tar.gz

     to explode and unpack.

     The difference is that the whole archive is compressed.  With
     `zip', archive members are archived individually.  `tar''s method
     yields better compression.  On the other hand, one can view the
     contents of a `zip' archive without having to decompress it.  As
     for the `tar' and `gzip' tandem, you need to decompress the
     archive to see its contents.  However, this may be done without
     needing disk space, by using pipes internally:

          tar tfz archive.tar.gz

     About corrupted compressed archives: `gzip''ed files have no
     redundancy, for maximum compression.  The adaptive nature of the
     compression scheme means that the compression tables are implicitly
     spread all over the archive.  If you lose a few blocks, the dynamic
     construction of the compression tables becomes unsychronized, and
     there is little chance that you could recover later in the archive.

     There are pending suggestions for having a per-volume or per-file
     compression in GNU `tar'.  This would allow for viewing the
     contents without decompression, and for resynchronizing
     decompression at every volume or file, in case of corrupted
     archives.  Doing so, we might loose some compressibility.  But
     this would have make recovering easier.  So, there are pros and
     cons.  We'll see!

`-Z'
`--compress'
`--uncompress'
     Filter the archive through `compress'.  Otherwise like `--gzip'
     (`-z').

`--use-compress-program=PROG'
     Filter through PROG (must accept `-d').