compact(1)                                                       compact(1)




 NAME    [Toc]    [Back]
      compact, uncompact, ccat - compact and uncompact files, and cat them

 SYNOPSIS    [Toc]    [Back]
      compact [name ...]

      uncompact [name ...]

      ccat [file ...]

 DESCRIPTION    [Toc]    [Back]
      compact compresses the named files using an adaptive Huffman code.  If
      no file names are given, standard input is compacted and sent to the
      standard output.  compact operates as an on-line algorithm.  Each time
      a byte is read, it is encoded immediately according to the current
      prefix code.  This code is an optimal Huffman code for the set of
      frequencies seen so far.  It is unnecessary to attach a decoding tree
      in front of the compressed file because the encoder and the decoder
      start in the same state and stay synchronized.  Furthermore, compact
      and uncompact can operate as filters.  In particular,

           ... | compact | uncompact | ...

      operates as a (very slow) no-op.

      When an argument file is given, it is compacted, the resulting file is
      placed in file.C, and file is unlinked.  The first two bytes of the
      compacted file code the fact that the file is compacted.  These bytes
      are used to prohibit recompaction.

      The amount of compression to be expected depends on the type of file
      being compressed.  Typical file size reduction (in percent) through
      compression are: Text, 38%; Pascal Source, 43%; C Source, 36%; and
      Binary, 19%.

      uncompact restores the original file from a file compressed by
      compact. If no file names are specified, standard input is uncompacted
      and sent to the standard output.

      ccat cats the original file from a file compressed by compact, without
      uncompressing the file.

    Access Control Lists (ACLs)    [Toc]    [Back]
      On systems that implement access control lists, when a new file is
      created with the effective user and group ID of the caller, the
      original file's ACL is copied to the new file after being altered to
      reflect any change in ownership (see acl(5) and aclv(5)).  In JFS file
      systems, files created by compact, uncompact or ccat do not inherit
      their parent directory's default ACL entries (if any), but instead
      retain their original ACLs.  When a file being compacted or
      uncompacted resides on a JFS file system, and the compacted or



 Hewlett-Packard Company            - 1 -   HP-UX 11i Version 2: August 2003






 compact(1)                                                       compact(1)




      uncompacted file resides on an HFS file system (or vice versa), as the
      result of ccat or the use of compact or uncompact as a filter,
      optional ACL entries are lost.

 WARNINGS    [Toc]    [Back]
      On short-filename systems, the last segment of the file name must
      contain 12 or fewer characters to allow space for the appended .C.

 DEPENDENCIES    [Toc]    [Back]
    NFS
      Access control list entries of networked files are summarized (as
      returned in st_mode by stat()), but not copied to the new file (see
      stat(2)).

 AUTHOR    [Toc]    [Back]
      compact was developed by Colin L. Mc Master.

 FILES    [Toc]    [Back]
      *.C       compacted file created by compact, removed by uncompact

 SEE ALSO    [Toc]    [Back]
      compress(1), pack(1), acl(5), aclv(5).

      Gallager, Robert G., ``Variations on a Theme of Huffman,'' I.E.E.E.
      Transactions on Information Theory, vol. IT-24, no. 6, November 1978,
      pp. 668 - 674.


 Hewlett-Packard Company            - 2 -   HP-UX 11i Version 2: August 2003