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GZIP(1)			    General Commands Manual		       GZIP(1)

       gzip, gunzip, zcat - compress or	expand files

       gzip [ -acdfhklLnNrtvV19	] [-S suffix] [	name ...  ]
       gunzip [	-acfhklLnNrtvV ] [-S suffix] [ name ...	 ]
       zcat [ -fhLV ] [	name ...  ]

       The  gzip  command 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 extension is 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  output.
       The  gzip command will only attempt to compress regular files.  In par-
       ticular,	it will	ignore symbolic	links.

       If the compressed file name is too long for its file system, gzip trun-
       cates  it.  The gzip command attempts to	truncate only the parts	of the
       file name longer	than 3 characters.  (A part is delimited 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  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 com-
       pressed	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	timestamp 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, or _z (ignoring case) 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 trun-
       cating 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
       and gunzip checks the uncompressed length. The standard compress	format
       was not designed	to allow consistency checks. However gunzip  is	 some-
       times  able  to	detect	a bad .Z file. If you get an error when	uncom-
       pressing	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 gen-
       erates  garbage	output.	  The  SCO compress -H format (lzh compression
       method) does not	include	a CRC but also allows some consistency checks.

       Files created by	zip can	be uncompressed	by gzip	only if	 they  have  a
       single  member  compressed with the 'deflation' method. This feature is
       only intended to	help conversion	of files to the	tar.gz format.
       To  extract a zip file with a single member, use	a command like 'gunzip
       <' or 'gunzip -S .zip'.  To extract zip files with  sev-
       eral members, use unzip instead of gunzip.

       The zcat	command	is identical to	gunzip -c.  (On	some systems, zcat may
       be installed as gzcat to	preserve the original link to compress.)  zcat
       uncompresses either a list of files on the command line or its standard
       input and writes	the uncompressed data on standard output.   zcat  will
       uncompress files	that have the correct magic number whether they	have a
       .gz suffix or not.

       The gzip	command	uses the Lempel-Ziv algorithm used in zip  and	PKZIP.
       The amount of compression obtained depends on the size of the input and
       the distribution	of common substrings.  Typically, text such as	source
       code  or	 English  is reduced by	60-70%.	 Compression is	generally much
       better than that	achieved by LZW	(as used in compress), Huffman	coding
       (as used	in pack), or adaptive Huffman coding (compact).

       Compression  is	always	performed,  even  if  the  compressed  file is
       slightly	larger than the	original. The worst case expansion  is	a  few
       bytes for the gzip file header, plus 5 bytes every 32K block, or	an ex-
       pansion ratio of	0.015% for large files.	Note that the actual number of
       used disk blocks	almost never increases.	 gzip preserves	the mode, own-
       ership and timestamps of	files when compressing or decompressing.

       -a --ascii
	      Ascii text mode: convert end-of-lines using  local  conventions.
	      This  option is supported	only on	some non-Unix systems. For MS-
	      DOS, CR LF is converted to LF when compressing, and LF  is  con-
	      verted to	CR LF when decompressing.

       -c --stdout --to-stdout
	      Write  output on standard	output;	keep original files unchanged.
	      If there are several input files,	the output consists of	a  se-
	      quence  of  independently	 compressed  members. To obtain	better
	      compression, concatenate	all  input  files  before  compressing

       -d --decompress --uncompress

       -f --force
	      Force compression	or decompression even if the file has multiple
	      links or the corresponding file already exists, or if  the  com-
	      pressed data is read from	or written to a	terminal. If the input
	      data is not in a format recognized by gzip, and  if  the	option
	      --stdout	is  also  given, copy the input	data without change to
	      the standard output: let zcat behave  as	cat.   If  -f  is  not
	      given,  and  when	not running in the background, gzip prompts to
	      verify whether an	existing file should be	overwritten.

       -h --help
	      Display a	help screen and	quit.

       -k --keep
	      Keep (don't delete) input	files during compression or decompres-

       -l --list
	      For each compressed file,	list the following fields:

		  compressed size: size	of the compressed file
		  uncompressed size: size of the uncompressed file
		  ratio: compression ratio (0.0% if unknown)
		  uncompressed_name: name of the uncompressed file

	      The  uncompressed	size is	given as -1 for	files not in gzip for-
	      mat, such	as compressed .Z files.	To get the  uncompressed  size
	      for such a file, you can use:

		  zcat file.Z |	wc -c

	      In  combination  with the	--verbose option, the following	fields
	      are also displayed:

		  method: compression method
		  crc: the 32-bit CRC of the uncompressed data
		  date & time: timestamp for the uncompressed file

	      The compression methods currently	supported  are	deflate,  com-
	      press,  lzh  (SCO	 compress  -H)	and pack.  The crc is given as
	      ffffffff for a file not in gzip format.

	      With --name, the uncompressed name,  date	and  time   are	 those
	      stored within the	compress file if present.

	      With  --verbose,	the  size totals and compression ratio for all
	      files is also displayed, unless some  sizes  are	unknown.  With
	      --quiet, the title and totals lines are not displayed.

       -L --license
	      Display the gzip license and quit.

       -n --no-name
	      When  compressing,  do not save the original file	name and time-
	      stamp by default.	(The original name is always saved if the name
	      had  to  be  truncated.)	When decompressing, do not restore the
	      original file name if present (remove only the gzip suffix  from
	      the  compressed file name) and do	not restore the	original time-
	      stamp if present (copy it	from the compressed file). This	option
	      is the default when decompressing.

       -N --name
	      When  compressing,  always save the original file	name and time-
	      stamp; this is the  default.  When  decompressing,  restore  the
	      original file name and timestamp if present. This	option is use-
	      ful on systems which have	a limit	on file	name  length  or  when
	      the timestamp has	been lost after	a file transfer.

       -q --quiet
	      Suppress all warnings.

       -r --recursive
	      Travel  the  directory structure recursively. If any of the file
	      names specified on the command line are directories,  gzip  will
	      descend  into  the directory and compress	all the	files it finds
	      there (or	decompress them	in the case of gunzip ).

       -S .suf --suffix	.suf
	      When compressing,	use suffix .suf	instead	of .gz.	 Any non-empty
	      suffix  can  be given, but suffixes other	than .z	and .gz	should
	      be avoided to avoid confusion  when  files  are  transferred  to
	      other systems.

	      When  decompressing,  add	 .suf  to the beginning	of the list of
	      suffixes to try, when deriving an	output file name from an input
	      file name.

	      Use  synchronous	output.	 With this option, gzip	is less	likely
	      to lose data during a system crash, but it can  be  considerably

       -t --test
	      Test. Check the compressed file integrity	then quit.

       -v --verbose
	      Verbose. Display the name	and percentage reduction for each file
	      compressed or decompressed.

       -V --version
	      Version. Display the version number and compilation options then

       -# --fast --best
	      Regulate	the  speed of compression using	the specified digit #,
	      where -1 or --fast  indicates  the  fastest  compression	method
	      (less  compression)  and -9 or --best indicates the slowest com-
	      pression method (best  compression).   The  default  compression
	      level is -6 (that	is, biased towards high	compression at expense
	      of speed).

	      When you synchronize a compressed	file  between  two  computers,
	      this  option  allows  rsync  to  transfer	 only  files that were
	      changed in the archive instead of	the entire archive.  Normally,
	      after  a change is made to any file in the archive, the compres-
	      sion algorithm can generate a new	version	of  the	 archive  that
	      does  not	 match	the  previous  version of the archive. In this
	      case, rsync transfers the	entire new version of the  archive  to
	      the  remote computer.  With this option, rsync can transfer only
	      the changed files	as well	as a small amount of metadata that  is
	      required	to  update  the	archive	structure in the area that was

       Multiple	compressed files can be	concatenated.  In  this	 case,	gunzip
       will extract all	members	at once. For example:

	     gzip -c file1  > foo.gz
	     gzip -c file2 >> foo.gz


	     gunzip -c foo

       is equivalent to

	     cat file1 file2

       In  case	of damage to one member	of a .gz file, other members can still
       be recovered (if	the damaged member is removed).	However, you  can  get
       better compression by compressing all members at	once:

	     cat file1 file2 | gzip > foo.gz

       compresses better than

	     gzip -c file1 file2 > foo.gz

       If you want to recompress concatenated files to get better compression,

	     gzip -cd old.gz | gzip > new.gz

       If a compressed file consists of	several	members, the uncompressed size
       and  CRC	reported by the	--list option applies to the last member only.
       If you need the uncompressed size for all members, you can use:

	     gzip -cd file.gz |	wc -c

       If you wish to create a single archive file with	 multiple  members  so
       that members can	later be extracted independently, use an archiver such
       as tar or zip. GNU tar supports the -z option to	invoke gzip  transpar-
       ently. gzip is designed as a complement to tar, not as a	replacement.

       The obsolescent environment variable GZIP can hold a set	of default op-
       tions for gzip.	These options are interpreted first and	can  be	 over-
       written	by  explicit command line parameters.  As this can cause prob-
       lems when using scripts,	this feature is	 supported  only  for  options
       that  are  reasonably likely to not cause too much harm,	and gzip warns
       if it is	used.  This feature will be removed in	a  future  release  of

       You can use an alias or script instead.	For example, if	gzip is	in the
       directory /usr/bin you can prepend $HOME/bin to your PATH and create an
       executable script $HOME/bin/gzip	containing the following:

	     #!	/bin/sh
	     export PATH=/usr/bin
	     exec gzip -9 "$@"

       znew(1),	zcmp(1), zmore(1), zforce(1), gzexe(1),	zip(1),	unzip(1), com-

       The gzip	file format is specified in P. Deutsch,	GZIP file format spec-
       ification version 4.3, <>, Internet
       RFC 1952	(May 1996).  The zip  deflation	 format	 is  specified	in  P.
       Deutsch,	 DEFLATE  Compressed  Data  Format  Specification version 1.3,
       <>, Internet	RFC 1951 (May 1996).

       Exit status is normally 0; if an	error occurs, exit status is 1.	 If  a
       warning occurs, exit status is 2.

       Usage: gzip [-cdfhklLnNrtvV19] [-S suffix] [file	...]
	      Invalid options were specified on	the command line.

       file: not in gzip format
	      The file specified to gunzip has not been	compressed.

       file: Corrupt input. Use	zcat to	recover	some data.
	      The  compressed  file has	been damaged. The data up to the point
	      of failure can be	recovered using

		    zcat file >	recover

       file: compressed	with xx	bits, can only handle yy bits
	      File was compressed (using LZW) by a  program  that  could  deal
	      with more	bits than the decompress code on this machine.	Recom-
	      press the	file with gzip,	which compresses better	and uses  less

       file: already has .gz suffix -- unchanged
	      The  file	 is assumed to be already compressed.  Rename the file
	      and try again.

       file already exists; do you wish	to overwrite (y	or n)?
	      Respond "y" if you want the output file to be replaced;  "n"  if

       gunzip: corrupt input
	      A	 SIGSEGV  violation  was detected which	usually	means that the
	      input file has been corrupted.

       xx.x% Percentage	of the input saved by compression.
	      (Relevant	only for -v and	-l.)

       -- not a	regular	file or	directory: ignored
	      When the input file is not a regular file	or directory, (e.g.  a
	      symbolic link, socket, FIFO, device file), it is left unaltered.

       -- has xx other links: unchanged
	      The  input  file has links; it is	left unchanged.	 See ln(1) for
	      more information.	Use the	-f flag	to force compression of	multi-
	      ply-linked files.

       When  writing  compressed  data to a tape, it is	generally necessary to
       pad the output with zeroes up to	a block	boundary.  When	 the  data  is
       read  and the whole block is passed to gunzip for decompression,	gunzip
       detects that there is extra trailing garbage after the compressed  data
       and emits a warning by default.	You can	use the	--quiet	option to sup-
       press the warning.

       The gzip	format represents the input size modulo	2^32,  so  the	--list
       option  reports incorrect uncompressed sizes and	compression ratios for
       uncompressed files 4 GB and larger.  To work around this	 problem,  you
       can  use	 the following command to discover a large uncompressed	file's
       true size:

	     zcat file.gz | wc -c

       The --list option reports sizes as -1 and crc as	ffffffff if  the  com-
       pressed file is on a non	seekable media.

       In  some	rare cases, the	--best option gives worse compression than the
       default compression level (-6). On some highly  redundant  files,  com-
       press compresses	better than gzip.

       Report bugs to:
       GNU gzip	home page: <>
       General help using GNU software:	<>

       Copyright (C) 1998-1999,	2001-2002, 2012, 2015-2021 Free	Software Foun-
       dation, Inc.
       Copyright (C) 1992, 1993	Jean-loup Gailly

       Permission is granted to	make and distribute verbatim  copies  of  this
       manual  provided	 the  copyright	 notice	and this permission notice are
       preserved on all	copies.

       Permission is granted to	copy and distribute modified versions of  this
       manual under the	conditions for verbatim	copying, provided that the en-
       tire resulting derived work is distributed under	the terms of a permis-
       sion notice identical to	this one.

       Permission  is granted to copy and distribute translations of this man-
       ual into	another	language, under	the above conditions for modified ver-
       sions,  except  that this permission notice may be stated in a transla-
       tion approved by	the Foundation.

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