COMPRESS(1) 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 pre-
served. If no file is specified, the standard input is com-
pressed onto the standard output.
Uncompress reverses the operation.
Zcat uncompresses the files, places the result on the stan-
dard 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 refer-
ence. 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 Compres-
sion,' IEEE Computer , 17 (1984) 8-19.