Manual Pages for UNIX Operating System command usage for man pcat

User Commands                                             pack(1)



NAME
     pack, pcat, unpack - compress and expand files

SYNOPSIS
     pack [-f/] [-] file...


     pcat file...


     unpack [-/] file...


DESCRIPTION
  pack
     The pack command attempts to store the specified files in  a
     compressed  form. Wherever possible (and useful), each input
     file file is replaced by a packed file file.z with the  same
     access  modes, access and modified dates, and owner as those
     of file. If pack is successful, file is removed.


     The amount of compression obtained depends on  the  size  of
     the  input  file  and  the character frequency distribution.
     Because a decoding tree forms the  first  part  of  each  .z
     file,  it  is  usually  not worthwhile to pack files smaller
     than three blocks, unless the character frequency  distribu-
     tion  is  very skewed, which can occur with printer plots or
     pictures.


     Typically, text files are reduced to 60-75% of their  origi-
     nal size. Load modules, which use a larger character set and
     have a more uniform distribution of characters, show  little
     compression, the packed versions being about 90% of the ori-
     ginal size.


     The pack utility returns a value that is the number of files
     that  it failed to compress. If that number exceeds 255, 255
     is returned.


     No packing occurs if:

         o    the file appears to be already packed

         o    the file name is too long to add the .z suffix

         o    the file has links

         o    the file is a directory



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User Commands                                             pack(1)



         o    the file cannot be opened

         o    the file is empty

         o    no disk storage blocks are saved by packing

         o    a file called file.z already exists

         o    the .z file cannot be created

         o    an I/O error occurred during processing.


     The last segment of the file name must be  short  enough  to
     allow space for the appended .zextension. Directories cannot
     be compressed.

  pcat
     The pcat command does for packed files what cat(1) does  for
     ordinary files, except that pcat cannot be used as a filter.
     The specified files are unpacked and written to the standard
     output.


     pcat returns the number of files it was  unable  to  unpack.
     Failure can occur if:

         o    the file cannot be opened;

         o    the file does not appear to be the output of pack.

  unpack
     The unpack command expands files created by pack.  For  each
     file  specified  in the command, a search is made for a file
     called file.z (or just file, if file ends in  .z).  If  this
     file  appears  to  be  a  packed file, it is replaced by its
     expanded version. The new file has the  .z  suffix  stripped
     from  its  name,  and  has the same access modes, access and
     modification dates, and owner as those of the packed file.


     unpack returns a value that is the number of  files  it  was
     unable  to  unpack.  Failure  can occur for the same reasons
     that it can in pcat, as well as for the following:

         o    a file with the unpacked name already exists;

         o    the unpacked file cannot be created.

OPTIONS
     The following options are supported by pack:




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User Commands                                             pack(1)



     -f    Forces packing of file. This is useful for causing  an
           entire  directory  to  be  packed  even if some of the
           files do not benefit. Packed files can be restored  to
           their original form using unpack or pcat.



     The following options are supported by pack and unpack:

     -/    When packing or unpacking, copies any ACL and extended
           system  attributes  associated with the source file to
           the target file. If an ACL or extended  system  attri-
           butes cannot be copied, the original file is retained,
           a diagnostic message is written  to  stderr,  and  the
           final exit status is non-zero.


OPERANDS
     The following operands are supported:

     file    A path name of a file to  be  packed,  unpacked,  or
             pcated; file can include or omit the .z suffix.


     -       pack uses Huffman (minimum redundancy)  codes  on  a
             byte-by-byte  basis.  If  the - argument is used, an
             internal flag is set that causes the number of times
             each  byte  is used, its relative frequency, and the
             code for the byte to be printed on the standard out-
             put.  Additional  occurrences  of - in place of file
             causes the internal flag to be set and reset.


USAGE
     See largefile(5) for the  description  of  the  behavior  of
     pack,  pcat, and unpack when encountering files greater than
     or equal to 2 Gbyte ( 2^31 bytes).

EXAMPLES
     Example 1 Viewing a Packed File


     To view a packed file named file.z use:



     example% pcat file.z



     or just:




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User Commands                                             pack(1)



     example% pcat file


     Example 2 Making and Unpacked Copy:


     To make an unpacked copy, say nnn, of a  packed  file  named
     file.z (without destroying file.z) use the command:



     example% pcat file >nnn


ENVIRONMENT VARIABLES
     See environ(5) for descriptions of the following environment
     variables  that  affect  the  execution  of  pack, pcat, and
     unpack: LC_CTYPE, LC_MESSAGES, and NLSPATH.

EXIT STATUS
     The following exit values are returned:

     0     Successful completion.


     >0    An error occurred. The number  of  files  the  command
           failed  to  pack/unpack  is returned. If the number of
           failures exceeds 255, then 255 is returned.


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



     ____________________________________________________________
    | ATTRIBUTE TYPE              | ATTRIBUTE VALUE             |
    |_____________________________|_____________________________|
    | Availability                | SUNWesu                     |
    |_____________________________|_____________________________|
    | CSI                         | Enabled                     |
    |_____________________________|_____________________________|


SEE ALSO
     cat(1),      compress(1),       zcat(1),       fgetattr(3C),
     fsetattr(3C)attributes(5), environ(5), largefile(5)







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