Skunkware 5/Skunkware 5.iso/man/cat.1/gzip.1

Text File | 1995-07-25 | 22KB | 463 lines

     GGGGZZZZIIIIPPPP((((1111))))               UUUUNNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((llllooooccccaaaallll))))               GGGGZZZZIIIIPPPP((((1111))))



     NNNNAAAAMMMMEEEE
          gzip, gunzip, zcat - compress or expand files

     SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
          ggggzzzziiiipppp [ ----aaaaccccddddffffhhhhllllLLLLnnnnNNNNrrrrttttvvvvVVVV11119999 ] [----SSSS ssssuuuuffffffffiiiixxxx] [ _n_a_m_e ... ]
          gggguuuunnnnzzzziiiipppp [ ----aaaaccccffffhhhhllllLLLLnnnnNNNNrrrrttttvvvvVVVV ] [----SSSS ssssuuuuffffffffiiiixxxx] [ _n_a_m_e ... ]
          zzzzccccaaaatttt [ ----ffffhhhhLLLLVVVV ] [ _n_a_m_e ... ]

     DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
          _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 ....ggggzzzz,,,, while keeping the same ownership
          modes, access and modification times.  (The default
          extension is ----ggggzzzz for VMS, zzzz 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.  _G_z_i_p 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,
          _g_z_i_p truncates it.  _G_z_i_p 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, _g_z_i_p keeps the original file name and timestamp
          in the compressed file. These are used when decompressing
          the file with the ----NNNN 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 _g_z_i_p -_d or _g_u_n_z_i_p or _z_c_a_t. 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.

          _g_u_n_z_i_p 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.  _g_u_n_z_i_p
          also recognizes the special extensions ....ttttggggzzzz and ....ttttaaaazzzz as
          shorthands for ....ttttaaaarrrr....ggggzzzz and ....ttttaaaarrrr....ZZZZ respectively.  When
          compressing, _g_z_i_p uses the ....ttttggggzzzz extension if necessary
          instead of truncating a file with a ....ttttaaaarrrr extension.

          _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, _c_o_m_p_r_e_s_s -_H or _p_a_c_k. The detection of the input
          format is automatic.  When using the first two formats,



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          _g_u_n_z_i_p checks a 32 bit CRC. For _p_a_c_k, _g_u_n_z_i_p checks the
          uncompressed length. The standard _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 uncompressing a .Z file, do not assume that the .Z file
          is correct simply because the standard _u_n_c_o_m_p_r_e_s_s does not
          complain. 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.  The SCO compress -H format (lzh compression method)
          does not include a CRC but also allows some consistency
          checks.

          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.gz 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 ----cccc.... (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 uncompress
          files that have the correct magic number whether they have a
          ....ggggzzzz 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.
          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 _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. Note that the actual number of used disk blocks
          almost never increases.  _g_z_i_p preserves the mode, ownership
          and timestamps of files when compressing or decompressing.


     OOOOPPPPTTTTIIIIOOOONNNNSSSS
          ----aaaa --------aaaasssscccciiiiiiii
               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 converted to CR LF when
               decompressing.

          ----cccc --------ssssttttddddoooouuuutttt --------ttttoooo----ssssttttddddoooouuuutttt



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               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.

          ----dddd --------ddddeeeeccccoooommmmpppprrrreeeessssssss --------uuuunnnnccccoooommmmpppprrrreeeessssssss
               Decompress.

          ----ffff --------ffffoooorrrrcccceeee
               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
               written to a terminal. If the input data is not in a
               format recognized by _g_z_i_p, and if the option --stdout
               is also given, copy the input data without change to
               the standard ouput: let _z_c_a_t behave as _c_a_t. If ----ffff is
               not given, and when not running in the background, _g_z_i_p
               prompts to verify whether an existing file should be
               overwritten.

          ----hhhh --------hhhheeeellllpppp
               Display a help screen and quit.

          ----llll --------lllliiiisssstttt
               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:

                   zcat 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.




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               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.

          ----LLLL --------lllliiiicccceeeennnnsssseeee
               Display the _g_z_i_p license and quit.

          ----nnnn --------nnnnoooo----nnnnaaaammmmeeee
               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 _g_z_i_p 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.

          ----NNNN --------nnnnaaaammmmeeee
               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.

          ----qqqq --------qqqquuuuiiiieeeetttt
               Suppress all warnings.

          ----rrrr --------rrrreeeeccccuuuurrrrssssiiiivvvveeee
               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 ).

          ----SSSS ....ssssuuuuffff --------ssssuuuuffffffffiiiixxxx ....ssssuuuuffff
               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 _p_a_c_k(1).

          ----tttt --------tttteeeesssstttt
               Test. Check the compressed file integrity.




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          ----vvvv --------vvvveeeerrrrbbbboooosssseeee
               Verbose. Display the name and percentage reduction for
               each file compressed or decompressed.

          ----VVVV --------vvvveeeerrrrssssiiiioooonnnn
               Version. Display the version number and compilation
               options then quit.

          ----#### --------ffffaaaasssstttt --------bbbbeeeesssstttt
               Regulate the speed of compression using the specified
               digit #, where ----1111 or --------ffffaaaasssstttt indicates the fastest
               compression method (less compression) and ----9999 or --------bbbbeeeesssstttt
               indicates the slowest compression method (best
               compression).  The default compression level is ----6666
               (that is, biased towards high compression at expense of
               speed).

     AAAADDDDVVVVAAAANNNNCCCCEEEEDDDD UUUUSSSSAAAAGGGGEEEE
          Multiple compressed files can be concatenated. In this case,
          _g_u_n_z_i_p 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:




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                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 transparently. gzip is
          designed as a complement to tar, not as a replacement.

     EEEENNNNVVVVIIIIRRRROOOONNNNMMMMEEEENNNNTTTT
          The environment variable GGGGZZZZIIIIPPPP 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="-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
          invocation of the program.

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

     DDDDIIIIAAAAGGGGNNNNOOOOSSSSTTTTIIIICCCCSSSS
          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.
          _f_i_l_e: not in gzip format
                  The file specified to _g_u_n_z_i_p has not been
                  compressed.
          _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 .gz suffix -- no change
                  The file is assumed to be already compressed.
                  Rename the file and try again.
          _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.



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          _x_x._x%
                  Percentage of the input saved by compression.
                  (Relevant only for ----vvvv and ----llll.)
          -- 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 ----ffff flag to force
                  compression of multiply-linked files.

     CCCCAAAAVVVVEEEEAAAATTTTSSSS
          When writing compressed data to a tape, it is generally
          necessary to pad the output with zeroes up to a block
          boundary. When the data is read and the whole block is
          passed to _g_u_n_z_i_p for decompression, _g_u_n_z_i_p detects that
          there is extra trailing garbage after the compressed data
          and emits a warning by default. You have to use the --quiet
          option to suppress the warning. This option can be set in
          the GGGGZZZZIIIIPPPP 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.)

     BBBBUUUUGGGGSSSS
          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, _c_o_m_p_r_e_s_s compresses better than
          _g_z_i_p.
















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