April 27, 2004 GZIP 1

### NAME

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

### SYNOPSIS

gzip [-cdfhlNnqrtVv] [-S suffix] file ] [[file ...] gunzip [-cfhNqrtVv] [-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 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.

-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 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 NetBSD1.3 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 NetBSD2.0.

This manual documents NetBSD gzip version 20040427.

### AUTHORS

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