GZIP(1)

NAME
gzip - compression/decompression tool using Lempel-Ziv coding (LZ77)

SYNOPSIS
gzip [-cdfhklNnqrtVv] [-S suffix] file [ file [...]]
gunzip [-cfhkNqrtVv] [-S suffix] file [ file [...]]
zcat [-fhV] file [ file [...]]

DESCRIPTION
The gzip program compresses and decompresses files using Lempel-Ziv coding (LZ77). If no files are specified, gzip will compress from standard input, or decompress to standard output. When in compression mode, each file will be replaced with another file with the suffix, set by the -S suffix option, added, if possible. In decompression mode, each file will be checked for existence, as will the file with the suffix added.

If invoked as gunzip then the -d option is enabled. If invoked as zcat or gzcat then both the -c and -d options are enabled.

This version of gzip is also capable of decompressing files compressed using pack(1), compress(1) or bzip2(1).

OPTIONS
The following options are available:

-1, --fast

-2

-3

-4

-5

-6

-7

-8

-9, --best
    These options change the compression level used, with the -1 option being the fastest, with less compression, and the -9 option being the slowest, with optimal compression. The default compression level is 6.

-c, --stdout, --to-stdout
    This option specifies that output will go to the standard output stream, leaving files intact.

-d, --decompress, --uncompress
    This option selects decompression rather than compression.

-f, --force
    This option turns on force mode. This allows files with multiple links, overwriting of pre-existing files, reading from or writing to a terminal, and when combined with the -c option, allowing non-compressed data to pass through unchanged.

-h, --help
    This option prints a usage summary and exits.

-k, --keep
    Keep (don't delete) input files during compression or decompression.

-l, --list
    This option displays information about the file's compressed and uncompressed size, ratio, uncompressed name. With the -v option, it also displays the compression method, CRC, date and time embedded in the file.

-N, --name
    This option causes the stored filename in the input file to be used as the output file.

-n, --no-name
    This option stops the filename and timestamp from being stored in the output file.

-q, --quiet
    With this option, no warnings or errors are printed.

-r, --recursive
    This option is used to gzip the files in a directory tree individually, using the fts(3) library.

-S suffix, --suffix suffix
    This option changes the default suffix from .gz to suffix.

-t, --test
    This option will test compressed files for integrity.

-V, --version
    This option prints the version of the gzip program.

-v, --verbose
    This option turns on verbose mode, which prints the compression ratio for each file compressed.

ENVIRONMENT
If the environment variable GZIP is set, it is parsed as a white-space separated list of options handled before any options on the command line. Options on the command line will override anything in GZIP.

SEE ALSO
bzip2(1), compress(1), fts(3), zlib(3)

HISTORY
The gzip program was originally written by Jean-loup Gailly, licensed under the GNU Public Licence. Matthew R. Green wrote a simple front end for NetBSD 1.3 distribution media, based on the freely re-distributable zlib library. It was enhanced to be mostly feature-compatible with the original GNU gzip program for NetBSD 2.0.

This manual documents NetBSD gzip version 20040427.

AUTHORS
This implementation of gzip was written by Matthew R. Green <mrg@eterna.com.au>.