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GZIP(1)                     General Commands ManualGZIP(1)NAME       gzip, gunzip, zcat - compress or expand filesSYNOPSIS       gzip [ -acdfhklLnNrtvV19 ] [-S suffix] [ name ...  ]       gunzip [ -acfhklLnNrtvV ] [-S suffix] [ name ...  ]       zcat [ -fhLV ] [ name ...  ]DESCRIPTION       Gzip  reduces  the  size  of  the  named  files using Lempel-Ziv coding       (LZ77).  Whenever possible, each file is replaced by one with  the  ex-       tension .gz, while keeping the same ownership modes, access and modifi-       cation 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.   Gzip       will  only  attempt  to compress regular files.  In particular, 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 ex-       ample, 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 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 tar.zip files to the tar.gz format.       To  extract  a zip file with a single member, use a command like gunzip       <foo.zip or gunzip -S .zip foo.zip.  To extract zip files with  several       members, use unzip instead of gunzip.       zcat  is  identical  to  gunzip  -c.  (On some systems, zcat may be in-       stalled as gzcat to preserve the original link to compress.)  zcat  un-       compresses  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.       Gzip uses the Lempel-Ziv algorithm used in zip and PKZIP.   The  amount       of  compression  obtained depends on the size of the input and the dis-       tribution 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.OPTIONS       -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              them.       -d --decompress --uncompress              Decompress.       -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-              sion.       -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.       --synchronous              Use  synchronous  output.  With this option, gzip is less likely              to lose data during a system crash, but it can  be  considerably              slower.       -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              quit.       -# --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).       --rsyncable              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              changed.ADVANCED USAGE       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       Then             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,       do:             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.ENVIRONMENT       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       gzip.       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 $HOME/bin/gzip containing the following:             #! /bin/sh             export PATH=/usr/bin             exec gzip -9 "$@"SEE ALSOznew(1),zcmp(1),zmore(1),zforce(1),gzexe(1),zip(1),unzip(1), com-press(1)       The gzip file format is specified in P. Deutsch, GZIP file format spec-       ification version 4.3, <https://www.ietf.org/rfc/rfc1952.txt>, Internet       RFC 1952 (May 1996).  The zip  deflation  format  is  specified  in  P.       Deutsch,  DEFLATE  Compressed  Data  Format  Specification version 1.3,       <https://www.ietf.org/rfc/rfc1951.txt>, Internet RFC 1951 (May 1996).DIAGNOSTICS       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              memory.       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              not.       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.  Seeln(1) for              more information. Use the -f flag to force compression of multi-              ply-linked files.CAVEATS       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.BUGS       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.COPYRIGHT NOTICE       Copyright (C) 1998-1999, 2001-2002, 2012, 2015-2018 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.                                     localGZIP(1)