pack man page on Xenix

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     PACK(C)		      XENIX System V		       PACK(C)

     Name
	  pack, pcat, unpack - Compresses and expands files.

     Syntax
	  pack [ - ] name ...

	  pcat name ...

	  unpack name ...

     Description
	  pack attempts to store the specified files in a compressed
	  form.	 Wherever possible, each input file name is replaced
	  by a packed file name.z with the same access modes, access
	  and modified dates, and the owner of name.  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 pack to display information about the file
	  compression.	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 scattered, 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 filename has more than 12 characters

	  -    The file has links

	  -    The file is a directory

	  -    The file cannot be opened

     Page 1					      (printed 2/7/91)

     PACK(C)		      XENIX System V		       PACK(C)

	  -    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 filename 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(C) does for ordinary
	  files.  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, enter the command:

	       pcat name >nnn

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

	  -    The filename (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 in a file where the
	  ``unpacked'' name already exists, or if the unpacked file
	  cannot be created.

     Page 2					      (printed 2/7/91)

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