term% cat index.txt COMPRESS(1) General Commands Manual COMPRESS(1)
NAME
compress, uncompress, zcat - compress and uncompress files
SYNOPSIS
compress [ option ] ... [ file ] ...
uncompress [ option ] ... [ file ] ...
zcat [ file ] ...
DESCRIPTION
Compress replaces each file with a compressed verison named file.Z.
Modes, dates, and (if possible) owner are preserved. If no file is
specified, the standard input is compressed onto the standard output.
Uncompress reverses the operation.
Zcat uncompresses the files, places the result on the standard output,
and leaves the files untouched.
The options are:
-c `uncompress -c' means `zcat'.
-d `compress -d' means `uncompress'.
-f (force) overwrite output file if it exists.
-F compress even if output is larger than input.
-b n use codes up to n bits long; see below.
-q (quiet) do not report compression ratios.
Compress uses the Lempel-Ziv algorithm given in the reference. Common
substrings in the file are replaced by 9-bit codes, then 10-bit codes,
and so on until the -b limit is reached. (The default of 16 can be
changed in the source to fit a smaller machine.) If the compression
ratio does not improve thereafter, compress starts afresh with 9-bit
codes.
DIAGNOSTICS
The exit status is 1 on error, 2 if the last file did not get smaller,
0 otherwise.
SEE ALSO
pack(1)
T. A. Welch, `A Technique for High Performance Data Compression,' IEEE
Computer , 17 (1984) 8-19.
COMPRESS(1)