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pack(1)                          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 will  be
       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
       distribution is very skewed, which may occur with printer plots or pic-
       tures.

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

       pack returns a value that is the number of files that it failed to com-
       press.

       No packing will occur if:

         o  the file appears to be already packed

         o  the file name has more than 14 - 2 bytes

         o  the file has links

         o  the file is a directory

         o  the file cannot be opened

         o  the file is empty

         o  no disk storage blocks will be 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 contain no  more  than  14  -  2
       bytes to allow space for the appended .z extension.  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  may
       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 speci-
       fied 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 modi-
       fication 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 may occur for the same reasons that it may in pcat, as
       well as for the following:

         o  a file with the ``unpacked'' name already exists;

         o  the unpacked file cannot be created.

         o  the filename (excluding the .z extension) has more than 14 bytes.


OPTIONS
       The following options are supported by pack:

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



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  output.  Additional
                       occurrences of - in place of file will cause the inter-
                       nal 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:
              example% pcat file


       Example 2: Making and Unpacked Copy:

       To make an unpacked copy, say nnn, of a packed file named file.z (with-
       out 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_MES-
       SAGES, 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.



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


       tab()    allbox;    cw(2.750000i)|     cw(2.750000i)     lw(2.750000i)|
       lw(2.750000i).    ATTRIBUTE   TYPEATTRIBUTE  VALUE  AvailabilitySUNWesu
       CSIEnabled


SEE ALSO
       cat(1), compress(1), zcat(1), attributes(5), environ(5), largefile( 5)



SunOS 5.10                        20 Dec 1996                          pack(1)