PACK(1)			 HP-UX 5.0		       PACK(1)

     NAME
	  pack, pcat, unpack - compress and expand files

     SYNOPSIS
	  pack [ - ] [ -f ] name ...

	  pcat name ...

	  unpack name ...

     HP-UX COMPATIBILITY
	  Level:    HP-UX/STANDARD

	  Origin:   System V

     DESCRIPTION
	  Pack attempts to store the specified files in	 a  compressed
	  form.	  Wherever possible (and useful), each input file name
	  is replaced by a packed file name.z  with  the  same	access
	  modes,  access  and  modified	 dates,	 and owner as those of
	  name.	 The -f option will force packing of  name.   This  is
	  useful  for causing an entire directory to be packed even if
	  some of the files will not benefit.  If pack is  successful,
	  name will be removed.	 Packed files can be restored to their
	  original form using unpack or pcat.

	  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  name  will	 cause the internal flag to be set and
	  reset.

	  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 pictures.

	  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 versions being about 90% of
	  the original size.

	  Pack returns a value that is the number  of  files  that  it
	  failed to compress.

	  No packing will occur if:
	       the file appears to be already packed;
	       the file is all nulls;
	       the file name has more than 12 characters;
	       the file has links;
	       the file is a directory;
	       the file cannot be opened;
	       no disk storage blocks will be saved by packing;
	       a file called name.z already exists;
	       the .z file cannot be created;
	       an I/O error occurred during processing.

	  The last segment of the file name must contain no more  than
	  12  characters to allow space for the appended .z extension.
	  Directories cannot be compressed.

	  Pcat does for packed files what  cat(1)  does	 for  ordinary
	  files,  except  that	pcat can not be used as a filter.  The
	  specified files are unpacked and  written  to	 the  standard
	  output.  Thus to view a packed file named name.z use:

	       pcat name.z

	  or just:

	       pcat name

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

	       pcat name >nnn

	  Pcat returns the number of files it was  unable  to  unpack.
	  Failure may occur if:

	       the file name (exclusive of the .z) has	more  than  12
	       characters;
	       the file cannot be opened;
	       the file does not appear to be the output of pack.

	  Unpack expands files created by pack.	 For  each  file  name
	  specified in the command, a search is made for a file called
	  name.z (or just name, if name 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 may occur for the same reasons
	  that it may in pcat, as well as for the following:

	       a file with the ``unpacked'' name already exists;
	       if the unpacked file cannot be created.

     SEE ALSO
	  cat(1).