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gzip (1)
  • >> gzip (1) ( Solaris man: Команды и прикладные программы пользовательского уровня )
  • gzip (1) ( FreeBSD man: Команды и прикладные программы пользовательского уровня )
  • gzip (1) ( Русские man: Команды и прикладные программы пользовательского уровня )
  • gzip (1) ( Linux man: Команды и прикладные программы пользовательского уровня )
  • gzip (8) ( Русские man: Команды системного администрирования )
  • 
    NAME
         gzip, gunzip, gzcat - compress or expand files
    
    SYNOPSIS
         gzip [ -acdfhlLnNrtvV19 ] [-S suffix] [ name ... ]
         gunzip [ -acfhlLnNrtvV ] [-S suffix] [ name ... ]
         gzcat [ -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 extension .gz, while keeping the same ownership
         modes,  access  and modification times.  (The default exten-
         sion 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  out-
         put.   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 truncates it.  Gzip attempts to truncate only the parts
         of the file name longer than 3 characters.  (A part is  del-
         imited  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  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 time stamp
         was not preserved after a file transfer.
    
         Compressed files can be  restored  to  their  original  form
         using gzip -d or gunzip or gzcat. 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 out-
         put.   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 zip files
         with several members, use unzip instead of gunzip.
    
         gzcat is identical to gunzip -c. (On some systems, zcat  may
         be  installed  as  gzcat  to  preserve  the original link to
         compress.) gzcat uncompresses either a list of files on  the
         command   line   or   its  standard  input  and  writes  the
         uncompressed data on standard output.  gzcat 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 distribution of common substrings.   Typi-
         cally,  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 expan-
         sion is a few bytes for the gzip file header, plus  5  bytes
         every  32K  block, or an expansion ratio of 0.015% for large
         files. Note that the  actual  number  of  used  disk  blocks
         almost  never increases.  gzip preserves the mode, ownership
         and timestamps of files when compressing or decompressing.
    
    
    OPTIONS
         -a --ascii
              Ascii text mode: convert end-of-lines using local  con-
              ventions.  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 out-
              put consists of a sequence 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 compressed data is read from or writ-
              ten 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 stan-
              dard ouput: let gzcat 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  format,  such  as compressed .Z files. To get the
              uncompressed size for such a file, you can use:
    
                  gzcat 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, 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 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 decompress-
              ing, 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 direc-
              tories,  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
              Use suffix .suf instead  of  .gz.  Any  suffix  can  be
              given,  but  suffixes  other  than .z and .gz should be
              avoided to avoid confusion 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 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 compres-
              sion).  The default compression level is -6  (that  is,
              biased towards high compression at expense of speed).
    
    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 indepen-
         dently, 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 replacement.
    
    ENVIRONMENT
         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 invo-
         cation of the program.
    
    SEE ALSO
         gznew(1), gzcmp(1), gzmore(1), gzforce(1), gzexe(1), zip(1),
         unzip(1), compress(1), pack(1)
    
    DIAGNOSTICS
         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 gzcat to recover some data.
                 The compressed file has been damaged. The data up to
                 the point of failure can be recovered using
                         gzcat 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 -- 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 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  direc-
                 tory,  (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.
    
    COPYRIGHT
         Copyright (C) 1987, 88, 89, 90, 91, 92, 1993  Free  Software
         Foundation, Inc.
    
         This program is  free  software;  you  can  redistribute  it
         and/or  modify  it under the terms of the GNU General Public
         License as published by the Free Software Foundation; either
         version 2, or (at your option) any later version.
    
         This program is distributed in the hope that it will be use-
         ful, but WITHOUT ANY WARRANTY; without even the implied war-
         ranty of MERCHANTABILITY or FITNESS FOR  A  PARTICULAR  PUR-
         POSE.  See the GNU General Public License for more details.
    
         You should have received a copy of the  GNU  General  Public
         License  along  with this program; if not, write to the Free
         Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
    
    CAVEATS
         When writing compressed data to  a  tape,  it  is  generally
         necessary  to pad the output with zeroes up to a block boun-
         dary. 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 warn-
         ing  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.)
    
    BUGS
         The --list option reports incorrect sizes if they  exceed  2
         gigabytes.  The --list option reports sizes as -1 and crc as
         ffffffff if the compressed 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,  compress  compresses  better  than
         gzip.
    
    NOTES
         Source for gzip is available in the SUNWgzipS package.
    
    
    
    


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