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Annotation of coherent/g/usr/bin/gzip/gzip.doc, revision 1.1

1.1     ! root        1: 
        !             2: GZIP(1)                  USER COMMANDS                    GZIP(1)
        !             3: 
        !             4: NAME
        !             5:      gzip, gunzip, zcat - compress or expand files
        !             6: 
        !             7: SYNOPSIS
        !             8:      gzip [ -cdfhLrtvV19 ] [ name ... ]
        !             9:      gunzip [ -cfhLrtvV ] [ name ... ]
        !            10:      zcat [ -hLV ] [ name ... ]
        !            11: 
        !            12: DESCRIPTION
        !            13:      Gzip reduces the size of the named  files  using  Lempel-Ziv
        !            14:      coding  (LZ77).  Whenever possible, each file is replaced by
        !            15:      one with the extension .z, while keeping the same  ownership
        !            16:      modes,  access and modification times.  (The extension is -z
        !            17:      for VMS, z for MSDOS, OS/2  and  Atari.)  If  no  files  are
        !            18:      specified,  the standard input is compressed to the standard
        !            19:      output. If the new file name is too long, gzip truncates  it
        !            20:      and  keeps  the  original  file name in the compressed file.
        !            21:      Gzip will only attempt to compress regular files.   In  par-
        !            22:      ticular, it will ignore symbolic links.
        !            23: 
        !            24:      Compressed files can be  restored  to  their  original  form
        !            25:      using gzip -d or gunzip or zcat.
        !            26: 
        !            27:      gunzip takes a  list  of  files  on  its  command  line  and
        !            28:      replaces  each  file whose name ends with .z or .Z or -z and
        !            29:      which  begins  with  the  correct  magic  number   with   an
        !            30:      uncompressed  file  without  the original extension.  gunzip
        !            31:      also recognizes the special  extensions  .tgz  and  .taz  as
        !            32:      shorthands for .tar.z or .tar.Z
        !            33: 
        !            34:      gunzip can currently decompress files created by gzip,  zip,
        !            35:      compress  or  pack.  The  detection  of  the input format is
        !            36:      automatic.  When using the first two formats, gunzip  checks
        !            37:      a  32  bit  CRC.  For  pack,  gunzip checks the uncompressed
        !            38:      length. The compress format was not designed to  allow  con-
        !            39:      sistency  checks. However gunzip is sometimes able to detect
        !            40:      a bad .Z file. If you get an error when uncompressing  a  .Z
        !            41:      file,  do  not  assume  that  the  .Z file is correct simply
        !            42:      because the standard uncompress does not complain. This gen-
        !            43:      erally means that the standard uncompress does not check its
        !            44:      input, and happily generates garbage output.
        !            45: 
        !            46:      Files created by zip can be uncompressed  by  gzip  only  if
        !            47:      they  have  a  single member compressed with the 'deflation'
        !            48:      method. This feature is only intended to help conversion  of
        !            49:      tar.zip files to the tar.z format. To extract zip files with
        !            50:      several members, use unzip instead of gunzip.
        !            51: 
        !            52:      zcat is identical to gunzip -c. (On some systems,  zcat  may
        !            53:      be  installed  as  gzcat  to  preserve  the original link to
        !            54:      compress.) zcat uncompresses either a list of files  on  the
        !            55:      command   line   or   its  standard  input  and  writes  the
        !            56: 
        !            57: Sun Release 4.1        Last change: local                       1
        !            58: 
        !            59: GZIP(1)                  USER COMMANDS                    GZIP(1)
        !            60: 
        !            61:      uncompressed data on standard output.  zcat will  uncompress
        !            62:      files that have the correct magic number whether they have a
        !            63:      .z suffix or not.
        !            64: 
        !            65:      Gzip uses the Lempel-Ziv algorithm used in  zip  and  PKZIP.
        !            66:      The  amount  of  compression obtained depends on the size of
        !            67:      the input and the distribution of common substrings.   Typi-
        !            68:      cally,  text  such  as  source code or English is reduced by
        !            69:      60-70%.  Compression is  generally  much  better  than  that
        !            70:      achieved  by  LZW  (as used in compress), Huffman coding (as
        !            71:      used in pack), or adaptive Huffman coding (compact).
        !            72: 
        !            73:      Compression is always performed, even if the compressed file
        !            74:      is  slightly larger than the original. The worst case expan-
        !            75:      sion is a few bytes for the gzip file header, plus  5  bytes
        !            76:      every  32K  block, or an expansion ratio of 0.015% for large
        !            77:      files.  gzip preserves the mode, ownership and timestamps of
        !            78:      files when compressing or decompressing.
        !            79: 
        !            80: OPTIONS
        !            81:      -c --stdout
        !            82:           Write output on standard output;  keep  original  files
        !            83:           unchanged.   If there are several input files, the out-
        !            84:           put consists of a sequence of independently  compressed
        !            85:           members.  To obtain better compression, concatenate all
        !            86:           input files before compressing them.
        !            87: 
        !            88:      -d --decompress
        !            89:           Decompress.
        !            90: 
        !            91:      -f --force
        !            92:           Force compression or decompression even if the file has
        !            93:           multiple   links  or  the  corresponding  file  already
        !            94:           exists.  If -f is not given, and when  not  running  in
        !            95:           the  background,  gzip  prompts  to  verify  whether an
        !            96:           existing file should be overwritten.
        !            97: 
        !            98:      -h --help
        !            99:           Display a help screen.
        !           100: 
        !           101:      -L --license
        !           102:           Display the gzip license.
        !           103: 
        !           104:      -q --quiet
        !           105:           Suppress all warnings.
        !           106: 
        !           107:      -r --recurse
        !           108:           Travel the directory structure recursively. If  any  of
        !           109:           the file names specified on the command line are direc-
        !           110:           tories,  gzip  will  descend  into  the  directory  and
        !           111:           compress  all  the  files it finds there (or decompress
        !           112: 
        !           113: Sun Release 4.1        Last change: local                       2
        !           114: 
        !           115: GZIP(1)                  USER COMMANDS                    GZIP(1)
        !           116: 
        !           117:           them in the case of gunzip ).
        !           118: 
        !           119:      -t --test
        !           120:           Test. Check the compressed file integrity.
        !           121: 
        !           122:      -v --verbose
        !           123:           Verbose. Display the name and percentage reduction  for
        !           124:           each file compressed.
        !           125: 
        !           126:      -V --version
        !           127:           Version. Display the  version  number  and  compilation
        !           128:           options.
        !           129: 
        !           130:      -# --fast --best
        !           131:           Regulate the speed of compression using  the  specified
        !           132:           digit  #,  where  -1  or  --fast  indicates the fastest
        !           133:           compression method (less compression) and -9 or  --best
        !           134:           indicates   the  slowest  compression  method  (optimal
        !           135:           compression).  The default compression level is -5.
        !           136: 
        !           137: ADVANCED USAGE
        !           138:      Multiple compressed files can be concatenated. In this case,
        !           139:      gunzip will extract all members at once. For example:
        !           140: 
        !           141:            gzip -c file1  > foo.z
        !           142:            gzip -c file2 >> foo.z Then
        !           143:            gunzip -c foo
        !           144: 
        !           145:      is equivalent to
        !           146: 
        !           147:            cat file1 file2
        !           148: 
        !           149:      In case of damage to one member of a .z file, other  members
        !           150:      can  still  be recovered (if the damaged member is removed).
        !           151:      However, you can get better compression by  compressing  all
        !           152:      members at once:
        !           153: 
        !           154:            cat file1 file2 | gzip > foo.z
        !           155: 
        !           156:      compresses better than
        !           157: 
        !           158:            gzip -c file1 file2 > foo.z
        !           159: 
        !           160:      If you want to recompress concatenated files to  get  better
        !           161:      compression, do:
        !           162: 
        !           163:            zcat old.z | gzip > new.z
        !           164: 
        !           165: ENVIRONMENT
        !           166:      The environment variable GZIP can  hold  a  set  of  default
        !           167:      options  for  gzip.  These options are interpreted first and
        !           168:      can be ovewritten by explicit command line  parameters.  For
        !           169: 
        !           170: Sun Release 4.1        Last change: local                       3
        !           171: 
        !           172: GZIP(1)                  USER COMMANDS                    GZIP(1)
        !           173: 
        !           174:      example:
        !           175:            for sh:    GZIP="-8 -v"; export GZIP
        !           176:            for csh:   setenv GZIP "-8 -v"
        !           177:            for MSDOS: set GZIP=-8 -v
        !           178: 
        !           179:      On  Vax/VMS,  the  name  of  the  environment  variable   is
        !           180:      GZIP_OPT,  to avoid a conflict with the symbol set for invo-
        !           181:      cation of the program.
        !           182: 
        !           183: SEE ALSO
        !           184:      znew(1), zcmp(1),  zmore(1),  zforce(1),  gzexe(1),  zip(1),
        !           185:      unzip(1), compress(1), pack(1), compact(1)
        !           186: 
        !           187: DIAGNOSTICS
        !           188:      Exit status is normally 0; if an error occurs,  exit  status
        !           189:      is 1. If a warning occurs, exit status is 2.
        !           190: 
        !           191:      Usage: gzip [-cdfhLrtvV19] [file ...]
        !           192:              Invalid options were specified on the command line.
        !           193:      file: not in gzip format
        !           194:              The  file  specified  to   gunzip   has   not   been
        !           195:              compressed.
        !           196:      file: Corrupt input. Use zcat to recover some data.
        !           197:              The compressed file has been damaged. The data up to
        !           198:              the point of failure can be recovered using
        !           199:                      zcat file > recover
        !           200:      file: compressed with xx bits, can only handle yy bits
        !           201:              File was compressed (using LZW) by  a  program  that
        !           202:              could  deal  with more bits than the decompress code
        !           203:              on this machine.  Recompress  the  file  with  gzip,
        !           204:              which compresses better and uses less memory.
        !           205:      file: already has z suffix -- no change
        !           206:              The  file  is  assumed  to  be  already  compressed.
        !           207:              Rename the file and try again or use zcat.
        !           208:      file already exists; do you wish to overwrite (y or n)?
        !           209:              Respond "y" if  you  want  the  output  file  to  be
        !           210:              replaced; "n" if not.
        !           211:      gunzip: corrupt input
        !           212:              A SIGSEGV violation was detected which usually means
        !           213:              that the input file has been corrupted.
        !           214:      xx.x%
        !           215:              Percentage  of  the  input  saved  by   compression.
        !           216:              (Relevant only for -v.)
        !           217:      -- not a regular file or directory: ignored
        !           218:              When the input file is not a regular file or  direc-
        !           219:              tory,  (e.g.  a  symbolic link, socket, FIFO, device
        !           220:              file), it is left unaltered.
        !           221:      -- has xx other links: unchanged
        !           222:              The input file has links; it is left unchanged.  See
        !           223:              ln(1) for more information. Use the -f flag to force
        !           224:              compression of multiply-linked files.
        !           225: 
        !           226: Sun Release 4.1        Last change: local                       4
        !           227: 
        !           228: GZIP(1)                  USER COMMANDS                    GZIP(1)
        !           229: 
        !           230: CAVEATS
        !           231:      The .z extension is already used by pack(1).  You  can  link
        !           232:      gzip  to  pcat to get transparent decompression for programs
        !           233:      expecting .z files to be in pack format.
        !           234: 
        !           235: Sun Release 4.1        Last change: local                       5
        !           236: 

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