(tar)Compressed Archives

Dealing with Compressed Archives

Compression

Compression

Creating and Reading Compressed Archives
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     *(This message will disappear, once this node revised.)*

   `--compress' (`-Z') indicates an archive stored in compressed format.
The `--compress' (`-Z') option is useful in saving time over networks
and space in pipes, and when storage space is at a premium.
`--compress' (`-Z') causes `tar' to compress when writing the archive,
or to uncompress when reading the archive.

   To perform compression and uncompression on the archive, `tar' runs
the `compress' utility.  `tar' uses the default compression parameters;
if you need to override them, avoid the `--compress' (`-Z') option and
run the `compress' utility explicitly.  It is useful to be able to call
the `compress' utility from within `tar' because the `compress' utility
by itself cannot access remote tape drives.

   The `--compress' (`-Z') option will not work in conjunction with the
`--multi-volume' (`-M') option or the `--append' (`-r'), `--update'
(`-u'), `--append' (`-r') and `--delete' operations.
FIXME: xref Modifying
   , for more information on these operations.

   If there is no compress utility available, `tar' will report an
error.

   `--compress-blocks' is like `--compress' (`-Z'), but when used in
conjunction with `--create' (`-c') also causes `tar' to pad the last
block of the archive out to the next block boundary as it is written.
This is useful with certain devices which require all write operations
be a multiple of a specific size.

     *Please Note:* The `compress' program may be covered by a patent,
     and therefore we recommend you stop using it.  We hope to have a
     different compress program in the future.  We may change the name
     of this option at that time.

`--compress'
`--uncompress'
`-z'
`-Z'
     When this option is specified, `tar' will compress (when writing
     an archive), or uncompress (when reading an archive).  Used in
     conjunction with the `--create' (`-c'), `--extract' (`-x'),
     `--list' (`-t') and `--compare' (`-d') operations.

`--compress-block'
`-z -z'
     Acts like `--compress' (`-Z'), but pads the archive out to the
     next block boundary as it is written when used in conjunction with
     the `--create' (`-c') operation.

FIXME: why not use -Z instead of -z -z ?