pack man page on HP-UX

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pack(1)								       pack(1)

       pack, pcat, unpack - compress and expand files using Huffman code




       attempts	 to  store the specified files in a compressed form.  Wherever
       possible, each input file name is replaced by a packed  file  with  the
       same  ownership,	 modes, and access and modification times.  The option
       forces packing of name.	This is useful for causing an entire directory
       to  be packed even if some of the files do not benefit.	If is success‐
       ful, name is removed.  Packed files can be restored to  their  original
       form using or

       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 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 file, it is usually not worthwhile to pack
       files smaller than three blocks unless the character frequency  distri‐
       bution is very skewed such as in 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 ver‐
       sions being about 90% of the original size.

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

       No packing occurs if:

	 ·  The file appears to be already packed.

	 ·  The file name has more than 12 characters and the file  system  is
	    configured as a short filename system.

	 ·  The file has links.

	 ·  The file is a directory.

	 ·  The file cannot be opened.

	 ·  The file is empty.

	 ·  No disk storage blocks will be saved by packing.

	 ·  A file called already exists.

	 ·  The file cannot be created.

	 ·  An I/O error occurred during processing.

       On short file name systems, the last segment of the file name must con‐
       tain no more than 12 characters to allow space for the appended	exten‐
       sion.  Directories cannot be compressed.

       does  for packed files what does for ordinary files, except that cannot
       be used as a filter.  The specified files are unpacked and  written  to
       the standard output.  Thus to view a packed file named use:

       or simply:

       To  make	 an  unpacked copy (named file) of a packed file named without
       destroying use the command:

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

	 ·  The file name (exclusive of the has more than 12 characters;

	 ·  The file cannot be opened;

	 ·  The file does not appear to have been created by pack.

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

       returns a value that is the number of files it was  unable  to  unpack.
       Failure	may occur for the reasons given for as well as for the follow‐

	 ·  A file with the "unpacked" name already exists;

	 ·  The unpacked file cannot be created.

   Access Control Lists (ACLs)
       retains all entries in a file's access control  list  when  compressing
       and expanding it (see acl(5)).

       Optional	 access control list entries of networked files are summarized
       (as returned in by but not copied to the new file (see stat(2)).

       This command is likely to be withdrawn from X/Open standards.  Applica‐
       tions  using  this command might not be portable to other vendors' sys‐
       tems.  Instead of it is recommended that you use the utility as it  has
       the following advantages:

	 ·  The	 algorithm  used to create the output files is frequently more
	    effective in reducing the size of files

	 ·  The compress utility can compress data from	 its  standard	input,
	    not just a named regular file.  Thus it is useful in pipelines

       is recommended instead of and, is recommended instead of

       cat(1), compact(1), compress(1), acl(5).


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