.TH COMPRESS 1
.SH NAME
compress, uncompress, zcat \- compress and uncompress files
.SH SYNOPSIS
.B compress
[ option ] ...
[ file ] ...
.PP
.B uncompress
[ option ] ... [ file ] ...
.PP
.B zcat
[ file ] ...
.SH DESCRIPTION
.I compress
replaces each
.I file
with a compressed verison named
.IB file .Z .
Modes, dates, and (if possible) owner are preserved.
If no
.I file
is specified, the standard input is compressed
onto the standard output.
.PP
.I Uncompress
reverses the operation.
.PP
.I Zcat
uncompresses the
.I files,
places the result on the
standard output, and leaves the files untouched.
.PP
The options are:
.TP
.B \-c
`uncompress \-c' means `zcat'.
.TP
.B \-d
`compress \-d' means `uncompress'.
.TP
.B \-f
(force) overwrite output file if it exists.
.TP
.B \-F
compress even if output is larger than input.
.TP
.BI \-b " n"
use codes up to
.I n
bits long; see below.
.TP
.B \-q
(quiet) do not report compression ratios.
.PP
.I 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 \-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,
.I compress
starts afresh with 9-bit codes.
.SH DIAGNOSTICS
The exit status is 1 on error, 2 if the last file did not get smaller,
0 otherwise.
.SH "SEE ALSO"
pack(1)
.br
T. A. Welch,
`A Technique for High Performance Data Compression,'
.I "IEEE Computer",
17 (1984) 8-19.