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Dd January 8, 2017
Dt GZIP 1
Os
Sh NAME
Nm gzip ,
Nm gunzip ,
Nm zcat
Nd compression/decompression tool using Lempel-Ziv coding (LZ77)
Sh SYNOPSIS
Nm
Op Fl cdfhlNnqrtVv
Op Fl S Ar suffix
Ar file
Oo
Ar file Oo ...
Oc
Oc
Nm gunzip
Op Fl cfhNqrtVv
Op Fl S Ar suffix
Ar file
Oo
Ar file Oo ...
Oc
Oc
Nm zcat
Op Fl fhV
Ar file
Oo
Ar file Oo ...
Oc
Oc
Sh DESCRIPTION
The
Nm
program compresses and decompresses files using Lempel-Ziv coding
(LZ77).
If no
Ar files
are specified,
Nm
will compress from standard input, or decompress to standard output.
When in compression mode, each
Ar file
will be replaced with another file with the suffix, set by the
Fl S Ar suffix
option, added, if possible.
In decompression mode, each
Ar file
will be checked for existence, as will the file with the suffix
added.
Pp
If invoked as
Nm gunzip
then the
Fl d
option is enabled.
If invoked as
Nm zcat
or
Nm gzcat
then both the
Fl c
and
Fl d
options are enabled.
Pp
This version of
Nm
is also capable of decompressing files compressed using
Xr compress 1 ,
Xr bzip2 1 ,
Ar lzip ,
or
Xr xz 1 .
Sh OPTIONS
The following options are available:
Bl -tag -width XXrXXXrecursiveX
It Fl 1 , Fl Fl fast
It Fl 2
It Fl 3
It Fl 4
It Fl 5
It Fl 6
It Fl 7
It Fl 8
It Fl 9 , Fl Fl best
These options change the compression level used, with the
Fl 1
option being the fastest, with less compression, and the
Fl 9
option being the slowest, with optimal compression.
The default compression level is 6.
It Fl c , Fl Fl stdout , Fl Fl to-stdout
This option specifies that output will go to the standard output
stream, leaving files intact.
It Fl d , Fl Fl decompress , Fl Fl uncompress
This option selects decompression rather than compression.
It Fl f , Fl Fl 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
Fl c
option, allowing non-compressed data to pass through unchanged.
It Fl h , Fl Fl help
This option prints a usage summary and exits.
It Fl k , Fl Fl keep
This option prevents
Nm
from deleting input files after (de)compression.
It Fl l , Fl Fl list
This option displays information about the file's compressed and
uncompressed size, ratio, uncompressed name.
With the
Fl v
option, it also displays the compression method, CRC, date and time
embedded in the file.
It Fl N , Fl Fl name
This option causes the stored filename in the input file to be used
as the output file.
It Fl n , Fl Fl no-name
This option stops the filename and timestamp from being stored in
the output file.
It Fl q , Fl Fl quiet
With this option, no warnings or errors are printed.
It Fl r , Fl Fl recursive
This option is used to
Nm
the files in a directory tree individually, using the
Xr fts 3
library.
It Fl S Ar suffix , Fl Fl suffix Ar suffix
This option changes the default suffix from .gz to
Ar suffix .
It Fl t , Fl Fl test
This option will test compressed files for integrity.
It Fl V , Fl Fl version
This option prints the version of the
Nm
program.
It Fl v , Fl Fl verbose
This option turns on verbose mode, which prints the compression
ratio for each file compressed.
El
Sh ENVIRONMENT
If the environment variable
Ev 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
Ev GZIP .
Sh EXIT STATUS
The
Nm
utility exits 0 on success,
1 on errors,
and 2 if a warning occurs.
Sh SIGNALS
Nm
responds to the following signals:
Bl -tag -width indent
It Dv SIGINFO
Report progress to standard error.
El
Sh SEE ALSO
Xr bzip2 1 ,
Xr compress 1 ,
Xr xz 1 ,
Xr fts 3 ,
Xr zlib 3
Sh HISTORY
The
Nm
program was originally written by Jean-loup Gailly, licensed under
the GNU Public Licence.
Matthew R. Green wrote a simple front end for
Nx 1.3
distribution media, based on the freely re-distributable zlib library.
It was enhanced to be mostly feature-compatible with the original
GNU
Nm
program for
Nx 2.0 .
Pp
This manual documents
Nx
Nm
version 20170803.
Sh AUTHORS
This implementation of
Nm
was written by
An Matthew R. Green Aq Mt [email protected] .

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