GZIP(1) USER COMMANDS GZIP(1)
NAME
gzip, gunzip, zcat - compress or expand files
SYNOPSIS
gzip [ -acdfhlLnNrtvV19 ] [-S suffix] [ name ... ]
gunzip [ -acfhlLnNrtvV ] [-S suffix] [ name ... ]
zcat [ -fhLV ] [ name ... ]
DESCRIPTION
Gzip reduces the size of the named files using Lempel-Ziv
coding (LZ77). Whenever possible, each file is replaced by
one with the extension .gz, while keeping the same ownership
modes, access and modification times. (The default exten-
sion is -gz for VMS, z for MSDOS, OS/2 FAT, Windows NT FAT
and Atari.) If no files are specified, or if a file name is
"-", the standard input is compressed to the standard out-
put. Gzip will only attempt to compress regular files. In
particular, it will ignore symbolic links.
If the compressed file name is too long for its file system,
gzip truncates it. Gzip attempts to truncate only the parts
of the file name longer than 3 characters. (A part is del-
imited by dots.) If the name consists of small parts only,
the longest parts are truncated. For example, if file names
are limited to 14 characters, gzip.msdos.exe is compressed
to gzi.msd.exe.gz. Names are not truncated on systems which
do not have a limit on file name length.
By default, gzip keeps the original file name and timestamp
in the compressed file. These are used when decompressing
the file with the -N option. This is useful when the
compressed file name was truncated or when the time stamp
was not preserved after a file transfer.
Compressed files can be restored to their original form
using gzip -d or gunzip or zcat. If the original name saved
in the compressed file is not suitable for its file system,
a new name is constructed from the original one to make it
legal.
gunzip takes a list of files on its command line and
replaces each file whose name ends with .gz, -gz, .z, -z, _z
or .Z and which begins with the correct magic number with an
uncompressed file without the original extension. gunzip
also recognizes the special extensions .tgz and .taz as
shorthands for .tar.gz and .tar.Z respectively. When
compressing, gzip uses the .tgz extension if necessary
instead of truncating a file with a .tar extension.
gunzip can currently decompress files created by gzip, zip,
compress, compress -H or pack. The detection of the input
format is automatic. When using the first two formats,
gunzip checks a 32 bit CRC. For pack, gunzip checks the
uncompressed length. The standard compress format was not
designed to allow consistency checks. However gunzip is
sometimes able to detect a bad .Z file. If you get an error
when uncompressing a .Z file, do not assume that the .Z file
is correct simply because the standard uncompress does not
complain. This generally means that the standard uncompress
does not check its input, and happily generates garbage out-
put. The SCO compress -H format (lzh compression method)
