OS/2 Professional/OS2PRO194.ISO/os2/packer/gzip/gzip.man

Text File | 1994-02-03 | 11.4 KB | 331 lines

GZIP(1)                                                   GZIP(1)


NNAAMMEE
       gzip, gunzip, zcat - compress or expand files

SSYYNNOOPPSSIISS
       ggzziipp [ --ccddffhhLLrrttvvVV1199 ] [ _n_a_m_e _._._.  ]
       gguunnzziipp [ --ccffhhLLrrttvvVV ] [ _n_a_m_e _._._.  ]
       zzccaatt [ --hhLLVV ] [ _n_a_m_e _._._.  ]

DDEESSCCRRIIPPTTIIOONN
       _G_z_i_p  reduces the size of the named files using Lempel-Ziv
       coding (LZ77).  Whenever possible, each file  is  replaced
       by  one with the extension ..zz,, while keeping the same own-
       ership modes, access and modification times.  (The  exten-
       sion  is  --zz for VMS, zz for MSDOS, OS/2 and Atari.)  If no
       files are specified, the standard input is  compressed  to
       the  standard  output.  If  the new file name is too long,
       _g_z_i_p truncates it and keeps the original file name in  the
       compressed file.  _G_z_i_p will only attempt to compress regu-
       lar files.  In particular, it will ignore symbolic  links.

       Compressed  files  can  be restored to their original form
       using _g_z_i_p _-_d or _g_u_n_z_i_p or _z_c_a_t_.

       _g_u_n_z_i_p takes a list of  files  on  its  command  line  and
       replaces each file whose name ends with ..zz or ..ZZ or --zz and
       which begins with the correct magic number with an  uncom-
       pressed  file without the original extension.  _g_u_n_z_i_p also
       recognizes the special extensions ..ttggzz and ..ttaazz as  short-
       hands for ..ttaarr..zz or ..ttaarr..ZZ

       _g_u_n_z_i_p  can  currently  decompress  files created by _g_z_i_p_,
       _z_i_p_, _c_o_m_p_r_e_s_s or _p_a_c_k_.  The detection of the input  format
       is  automatic.   When  using the first two formats, _g_u_n_z_i_p
       checks a 32 bit CRC. For _p_a_c_k_, _g_u_n_z_i_p  checks  the  uncom-
       pressed  length.  The  _c_o_m_p_r_e_s_s format was not designed to
       allow consistency checks. However _g_u_n_z_i_p is sometimes able
       to  detect  a bad .Z file. If you get an error when uncom-
       pressing a .Z file, do not assume that the .Z file is cor-
       rect  simply because the standard _u_n_c_o_m_p_r_e_s_s does not com-
       plain. This generally means that the  standard  _u_n_c_o_m_p_r_e_s_s
       does  not  check  its input, and happily generates garbage
       output.

       Files created by _z_i_p 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.z format. To extract zip files
       with several members, use _u_n_z_i_p instead of _g_u_n_z_i_p_.

       _z_c_a_t is identical to _g_u_n_z_i_p --cc..  (On  some  systems,  _z_c_a_t
       may be installed as _g_z_c_a_t to preserve the original link to
       _c_o_m_p_r_e_s_s_._)  _z_c_a_t uncompresses either a list  of  files  on
       the  command  line  or  its  standard input and writes the
       uncompressed  data  on   standard   output.    _z_c_a_t   will



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GZIP(1)                                                   GZIP(1)


       uncompress  files  that  have  the  correct  magic  number
       whether they have a ..zz suffix or not.

       _G_z_i_p uses the Lempel-Ziv algorithm used in _z_i_p and  PKZIP.
       The  amount of compression obtained depends on the size of
       the input and the distribution of common substrings.  Typ-
       ically,  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 _c_o_m_p_r_e_s_s), Huffman coding (as
       used in _p_a_c_k), or adaptive Huffman coding (_c_o_m_p_a_c_t).

       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.   _g_z_i_p  preserves  the  mode,  ownership  and
       timestamps of files when compressing or decompressing.


OOPPTTIIOONNSS
       --cc ----ssttddoouutt
              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.

       --dd ----ddeeccoommpprreessss
              Decompress.

       --ff ----ffoorrccee
              Force compression or decompression even if the file
              has   multiple  links  or  the  corresponding  file
              already exists.  If --ff is not given, and  when  not
              running  in  the background, _g_z_i_p prompts to verify
              whether an existing file should be overwritten.

       --hh ----hheellpp
              Display a help screen.

       --LL ----lliicceennssee
              Display the _g_z_i_p license.

       --qq ----qquuiieett
              Suppress all warnings.

       --rr ----rreeccuurrssee
              Travel the directory structure recursively. If  any
              of the file names specified on the command line are
              directories, _g_z_i_p will descend into  the  directory
              and  compress  all  the  files  it  finds there (or
              decompress them in the case of _g_u_n_z_i_p ).




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GZIP(1)                                                   GZIP(1)


       --tt ----tteesstt
              Test. Check the compressed file integrity.

       --vv ----vveerrbboossee
              Verbose. Display the name and percentage  reduction
              for each file compressed.

       --VV ----vveerrssiioonn
              Version. Display the version number and compilation
              options.

       --## ----ffaasstt ----bbeesstt
              Regulate the speed of compression using the  speci-
              fied  digit  _#,  where  --11  or ----ffaasstt indicates the
              fastest compression method (less  compression)  and
              --99  or  ----bbeesstt  indicates  the  slowest compression
              method (optimal compression).  The default compres-
              sion level is --55..

AADDVVAANNCCEEDD UUSSAAGGEE
       Multiple  compressed  files  can  be concatenated. In this
       case, _g_u_n_z_i_p will extract all members at once.  For  exam-
       ple:

             gzip -c file1  > foo.z
             gzip -c file2 >> foo.z Then
             gunzip -c foo

       is equivalent to

             cat file1 file2

       In  case  of damage to one member of a .z file, other mem-
       bers can still be recovered  (if  the  damaged  member  is
       removed).  However, you can get better compression by com-
       pressing all members at once:

             cat file1 file2 | gzip > foo.z

       compresses better than

             gzip -c file1 file2 > foo.z

       If you want to recompress concatenated files to get better
       compression, do:

             zcat old.z | gzip > new.z

EENNVVIIRROONNMMEENNTT
       The  environment  variable  GGZZIIPP can hold a set of default
       options for _g_z_i_p_.  These options are interpreted first and
       can  be  overwritten  by explicit command line parameters.
       For example:
             for sh:    GZIP="-8 -v"; export GZIP



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GZIP(1)                                                   GZIP(1)


             for csh:   setenv GZIP "-8 -v"
             for MSDOS: set GZIP=-8 -v

       On Vax/VMS,  the  name  of  the  environment  variable  is
       GZIP_OPT,  to  avoid  a  conflict  with the symbol set for
       invocation of the program.

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

DDIIAAGGNNOOSSTTIICCSS
       Exit status is normally 0; if an error occurs, exit status
       is 1. If a warning occurs, exit status is 2.

       Usage: gzip [-cdfhLrtvV19] [file ...]
               Invalid options  were  specified  on  the  command
               line.
       _f_i_l_e: not in gzip format
               The  file  specified  to  _g_u_n_z_i_p has not been com-
               pressed.
       _f_i_l_e_: 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
       _f_i_l_e: compressed with _x_x bits, can only handle _y_y bits
               _F_i_l_e  was compressed (using LZW) by a program that
               could deal with more _b_i_t_s than the decompress code
               on  this  machine.  Recompress the file with gzip,
               which compresses better and uses less memory.
       _f_i_l_e: already has z suffix -- no change
               The file is  assumed  to  be  already  compressed.
               Rename the file and try again or use zcat.
       _f_i_l_e 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.
       _x_x_._x_%
               Percentage  of  the  input  saved  by compression.
               (Relevant only for --vv.)
       -- 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 _x_x other links: unchanged
               The input file has links; it  is  left  unchanged.
               See _l_n(1) for more information. Use the --ff flag to
               force compression of multiply-linked files.

CCAAVVEEAATTSS
       The .z extension is already used by _p_a_c_k(1)_.  You can link
       _g_z_i_p to _p_c_a_t to get transparent decompression for programs



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GZIP(1)                                                   GZIP(1)


       expecting .z files to be in _p_a_c_k format.
























































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