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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
       particular, it will ignore symbolic links.

       If the compressed file name is too long for its file system, gzip
       truncates 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
       compressed 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 valid.

       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
       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
       and 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 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
       several 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 per 32 KiB block, or an
       expansion ratio of 0.015% for large files.  The actual number of used
       disk blocks almost never increases.

       gzip normally preserves the mode and modification timestamp of a file
       when compressing or decompressing.  If you have appropriate privileges,
       it also preserves the file's owner and group.


       -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
              converted 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
              compressed 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

       -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
              format, 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,
              compress, 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
              timestamp 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
              timestamp 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 save
              the seconds part of the original modification timestamp if the
              original is a regular file and its timestamp is at least 1
              (1970-01-01 00:00:01 UTC) and is less than 2**32 (2106-02-07
              06:28:16 UTC, assuming leap seconds are not counted); this is
              the default.  When decompressing, restore from the saved file
              name and timestamp if present.  This option is useful 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 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
              compression 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
              compression 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.


       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
       transparently.  gzip is designed as a complement to tar, not as a


       The obsolescent 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.  As this can cause
       problems 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),

       The gzip file format is specified in P. Deutsch, GZIP file format
       specification 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

                    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.
              Recompress 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

       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 can use the --quiet option to
       suppress the warning.


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


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


       Copyright (C) 1998-1999, 2001-2002, 2012, 2015-2023 Free Software
       Foundation, 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
       entire resulting derived work is distributed under the terms of a
       permission notice identical to this one.

       Permission is granted to copy and distribute translations of this
       manual into another language, under the above conditions for modified
       versions, except that this permission notice may be stated in a
       translation approved by the Foundation.

                                     local                             gzip(1)

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