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GZIP(1) 							       GZIP(1)

       gzip, gunzip, zcat - compress or expand files

       gzip [ -acdfhlLnNrtvV19 ] [-S suffix] [ name ...  ]
       gunzip [ -acfhlLnNrtvV ] [-S suffix] [ name ...	]
       zcat [ -fhLV ] [ name ...  ]

       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 modi
       fication times.	(The default extension 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
       output.	Gzip will only attempt to compress regular files.  In particu
       lar, it will ignore symbolic links.

       If the compressed file name is too long for its file system, gzip trun
       cates  it.   Gzip  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 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 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 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	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 tar.zip files to the tar.gz format.
       To  extract  a zip file with a single member, use a command like gunzip
       , Inter
       net 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).

       -a --ascii
	      Ascii  text  mode: convert end-of-lines using local conventions.
	      This option is supported only  on  some  non-Unix  systems.  For
	      MSDOS, 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
	      sequence 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 ouput: 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.

       -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: time stamp 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  time stamp if present. This option is
	      useful on systems which have a limit on file name length or when
	      the time stamp 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 ).

	      While compressing, synchronize the output occasionally based  on
	      the  input.   This  increases  size  by less than 1 percent most
	      cases, but means that the rsync(1) program can much  more  effi
	      ciently  synchronize  files  compressed  with this flag.	gunzip
	      cannot tell the difference between  a  compressed  file  created
	      with this option, and one created without it.

       -S .suf --suffix .suf
	      Use  suffix  .suf  instead  of .gz. Any suffix can be given, but
	      suffixes other than .z and .gz should be avoided to avoid confu
	      sion when files are transferred to other systems.  A null suffix
	      forces  gunzip  to   try	decompression  on  all	 given	 files
	      regardless of suffix, as in:

		  gunzip -S "" *       (*.* for MSDOS)

	      Previous	versions  of gzip used the .z suffix. This was changed
	      to avoid a conflict with pack(1).

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

       -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).

       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 environment variable GZIP can hold a set  of  default  options  for
       gzip.   These  options  are interpreted first and can be overwritten by
       explicit command line parameters. For example:
	     for sh:	GZIP="-8v --name"; export GZIP
	     for csh:	setenv GZIP "-8v --name"
	     for MSDOS: set GZIP=-8v --name

       On Vax/VMS, the name of the environment variable is GZIP_OPT, to  avoid
       a conflict with the symbol set for invocation of the program.

       znew(1), zcmp(1), zmore(1), zforce(1), gzexe(1), zip(1), unzip(1), com
       press(1), pack(1), compact(1)

       The gzip file format is specified in P. Deutsch, GZIP file format spec
       ification version 4.3, , Inter
       net 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 [-cdfhlLnNrtvV19] [-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 -- no change
	      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
	      multiply-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 have to use the --quiet option to
       suppress the warning. This option can be set in	the  GZIP  environment
       variable as in:
	 for sh:  GZIP="-q"  tar -xfz --block-compress /dev/rst0
	 for csh: (setenv GZIP -q; tar -xfz --block-compr /dev/rst0

       In  the	above  example, gzip is invoked implicitly by the -z option of
       GNU tar. Make sure that the same block size (-b option of tar) is  used
       for  reading  and  writing  compressed  data  on  tapes.  (This example
       assumes you are using the GNU version of tar.)

       The gzip format represents the 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 uncom
       pressed files 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.

       Copyright  1998, 1999, 2001, 2002 Free Software Foundation, Inc.
       Copyright  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
       entire  resulting derived work is distributed under the terms of a per
       mission 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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