gzip.doc

gzip1.2.4源码

          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
     znew(1), zcmp(1),  zmore(1),  zforce(1),  gzexe(1),  zip(1),
     unzip(1), compress(1), pack(1), compact(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 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.  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.

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  compres-
     sion than the default compression level (-6). On some highly
     redundant files, compress compresses better than gzip.