compress(C)                     19 June 1992                     compress(C)


 Name

    compress, uncompress, zcat - compress data for storage, uncompress and
    display compressed files

 Syntax

    compress [ -cdfFqv ] [ -b bits ] file
    compress -P fd
    uncompress [ -fqc ] file
    uncompress [ -P fd ]
    zcat file

 Description

    The compress command takes a file and compresses it to a smaller size
    (without loss of information), creates a compressed output file, and
    removes the original file unless the -c option is present.  Compression
    is achieved by encoding common strings within the file.  uncompress
    restores a previously compressed file to its uncompressed state and
    removes the compressed version.  zcat uncompresses and displays a file on
    the standard output.

    If the -P fd option is specified, compress reads a list of file names
    from the pipe associated with the file descriptor fd. One filename is
    read from each successive 1 K block of data in the pipe.  Each filename
    is null terminated.  File names are read until a null character is
    encountered at the beginning of a block or the pipe is closed.  Each file
    is then compressed.  The output files have the same name as, and
    overwrite, the original files.  This option can also be used with
    uncompress.

    If no file is specified on the command line, input is taken from the
    standard input and the output is directed to the standard output. Output
    defaults to a file with the same filename as the input file with the suf-
    fix ``.Z'' or it can be directed through the standard output. The output
    files have the same permissions and ownership as the corresponding input
    files or the user's standard permissions if output is directed through
    the standard output.

    If no space is saved by compression, the output file is not written
    unless the -F flag is present on the command line.

    If you attempt to compress a symbolic link, the link will be broken and a
    compressed copy of the file to which the symbolic link pointed will be
    created locally.  compress will fail on a file with hard (non-symbolic)
    links.

 Options

    The following options are available from the command line:

    -b bits Specifies the maximum number of bits to use in encoding.

    -c      Writes output on the standard output and does not remove original
            file.

    -d      Decompresses a compressed file.

    -f      Overwrites previous output file.

    -F      Writes output file even if compression saves no space.

    -q      Generates no output except error messages, if any.

    -v      Prints the name of the file being compressed, the percentage of
            compression achieved.  With uncompress, the name of of the
            uncompressed file is printed.

 Notes

    The -P option is provided for internal use by tar(C).

    the -v option is not compatible with the -c option.

 See also

    ar(CP), cat(C) pack(C), tar(C)

 Value added

    compress, uncompress and zcat are extensions of AT&T System V provided by
    The Santa Cruz Operation, Inc.