compress, uncompress, zcat - compress, uncompress  files  or
     display expanded files


     compress [-fv] [-b bits] [file...]

     compress [-cfv] [-b bits] [file]

     uncompress [-cfv] [file...]

     zcat [file...]


     The compress utility will attempt to reduce the size of  the
     named files by using adaptive Lempel-Ziv coding. Except when
     the output is to the standard  output,  each  file  will  be
     replaced  by  one  with  the extension .Z, while keeping the
     same ownership modes, change times and  modification  times.
     If  appending  the  .Z  to  the file pathname would make the
     pathname exceed 1023 bytes, the command  will  fail.  If  no
     files  are  specified, the standard input will be compressed
     to the standard output.

     The amount of compression obtained depends on  the  size  of
     the input, the number of bits per code, and the distribution
     of common substrings. Typically, text such as source code or
     English  is reduced by 50-60%. Compression is generally much
     better than that achieved by  Huffman  coding  (as  used  in
     pack(1)) and it takes less time to compute. The bits parame-
     ter specified  during  compression  is  encoded  within  the
     compressed  file,  along  with a magic number to ensure that
     neither decompression of random data  nor  recompression  of
     compressed data is subsequently allowed.

     The uncompress utility will restore files to their  original
     state  after  they  have  been compressed using the compress
     utility. If no files are specified, the standard input  will
     be uncompressed to the standard output.

     This utility supports the uncompressing of  any  files  pro-
     duced  by  compress. For files produced by compress on other
     systems, uncompress supports 9- to 16-bit  compression  (see

     The  zcat  utility  will  write  to  standard   output   the
     uncompressed  form  of files that have been compressed using
     compress. It is the equivalent of uncompress -c. Input files
     are not affected.


     The following options are supported:

          -c    Writes to  the  standard  output;  no  files  are
                changed and no .Z files are created. The behavior
                of zcat is identical to that of `uncompress -c'.

          -f    When compressing,  forces  compression  of  file,
                even  if  it does not actually reduce the size of
                the file, or if  the  corresponding  file.Z  file
                already  exists.  If  the -f option is not given,
                and the process is not running in the background,
                prompts to verify whether an existing file.Z file
                should be overwritten.  When uncompressing,  does
                not  prompt  for  overwriting  files.  If  the -f
                option is not given, and the process is not  run-
                ning in the background, prompts to verify whether
                an existing file should be  overwritten.  If  the
                standard  input  is  not a terminal and -f is not
                given, writes a diagnostic  message  to  standard
                error and exits with a status greater than 0.

          -v    Verbose. Writes to standard error  messages  con-
                cerning  the percentage reduction or expansion of
                each file.

          -b bits
                Sets the upper limit (in bits)  for  common  sub-
                string  codes.  bits must be between 9 and 16 (16
                is the default). Lowering the number of bits will
                result in larger, less compressed files.


     The following operand is supported:

          file  A path  name  of  a  file  to  be  compressed  by
                compress,  uncompressed  by  uncompress, or whose
                uncompressed form is written to standard  out  by
                zcat.  If  file is -, or if no file is specified,
                the standard input will be used.


     See largefile(5) for the  description  of  the  behavior  of
     compress,  uncompress,  and  zcat  when  encountering  files
     greater than or equal to 2 Gbyte ( 2**31 bytes).


     See environ(5) for descriptions of the following environment
     variables that affect the execution of compress, uncompress,
     and  zcat:  LANG,  LC_ALL,  LC_CTYPE,    LC_MESSAGES,    and


     The following error values are returned:

     0     Successful completion.

     1     An error occurred.

     2     One or more files were  not  compressed  because  they
           would  have  increased  in size (and the -f option was
           not specified).

     >2    An error occurred.


     See attributes(5) for descriptions of the  following  attri-

    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    | Availability                | SUNWesu                     |
    | CSI                         | Enabled                     |
    | Interface Stability         | Standard                    |


     ln(1),  pack(1),  attributes(5),  environ(5),  largefile(5),


     Usage: compress [-fvc] [-b maxbits] [file... ]
           Invalid options were specified on the command line.

     Missing maxbits
           Maxbits must follow -b,  or  invalid  maxbits,  not  a
           numeric value.

     file: not in compressed format
           The  file  specified  to  uncompress  has   not   been

     file: compressed with xxbits, can only handle yybits
           file was compressed by a program that could deal  with
           more  bits  than  the  compress  code on this machine.
           Recompress the file with smaller bits.

     file: already has .Z 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.

     uncompress: corrupt input
           A SIGSEGV violation was detected, which usually  means
           that the input file is corrupted.

     Compression:  xx.xx%
           Percentage  of  the  input   saved   by   compression.
           (Relevant only for -v.)

     - - not a regular file: unchanged
           When the input file is not a regular file, (such as  a
           directory), it is left unaltered.

     - - has xx other links: unchanged
           The input file has links; it is left  unchanged.   See
           ln(1) for more information.

     - - file unchanged
           No savings are  achieved  by  compression.  The  input
           remains uncompressed.

     filename too long to tack on .Z
           The path name is too long to append the .Z suffix.


     Although compressed files are  compatible  between  machines
     with large memory, -b 12 should be used for file transfer to
     architectures with a  small  process  data  space  (64KB  or

     compress should be more flexible about the existence of  the
     .Z suffix.

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