pack man page on SmartOS

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PACK(1)								       PACK(1)

       pack, pcat, unpack - compress and expand files

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

       pcat file...

       unpack [-/] file...

       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

       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 can occur with printer plots or pic‐

       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.

       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

	   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.

       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.

       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 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.

       The following options are supported by pack:

	     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 attributes cannot be copied, the origi‐
	     nal  file is retained, a diagnostic message is written to stderr,
	     and the final exit status is non-zero.

       The following operands are supported:

	       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 fre‐
	       quency, and the code for the byte to be printed on the standard
	       output. Additional occurrences of − in place of file causes the
	       internal flag to be set and reset.

       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

       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

       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.

       The following exit values are returned:

	     Successful completion.

	     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.

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

       │CSI	       │ Enabled	 │

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

				 Mar 13, 2008			       PACK(1)

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