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    Command:

    zcat

    
    
    

    SYNOPSIS

           gzip [ -acdfhlLnNrtvV19 ] [-S suffix] [ name ...  ]
           gunzip [ -acfhlLnNrtvV ] [-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
           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.
    
           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
           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.
    
           The gzip file format is specified in P. Deutsch, GZIP file format spec-
           ification version 4.3, <ftp://ftp.isi.edu/in-notes/rfc1952.txt>, Inter-
           net RFC 1952 (May 1996).  The zip deflation format is specified  in  P.
           Deutsch,  DEFLATE  Compressed  Data  Format  Specification version 1.3,
           <ftp://ftp.isi.edu/in-notes/rfc1951.txt>, Internet RFC 1951 (May 1996).
    
    
    

    OPTIONS

           -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
                  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.
    
                  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 ).
    
           -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.
    
                  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).
    
    
    

    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.
    
    
           The gzip file format is specified in P. Deutsch, GZIP file format spec-
           ification version 4.3, <ftp://ftp.isi.edu/in-notes/rfc1952.txt>, Inter-
           net  RFC  1952 (May 1996).  The zip deflation format is specified in P.
           Deutsch, DEFLATE Compressed  Data  Format  Specification  version  1.3,
           <ftp://ftp.isi.edu/in-notes/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 [-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
                  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 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.
    
           for reading and  writing  compressed  data  on  tapes.   (This  example
           assumes you are using the GNU version of tar.)
    
    
    

    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 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  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.
    
                                         local                             GZIP(1)
    
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