NAME

       rzip - a large-file compression program

SYNOPSIS

       rzip [OPTIONS] <files...>

DESCRIPTION

       rzip  is  a file compression program designed to do particularly well on very large files containing long
       distance redundancy.

OPTIONS SUMMARY

       Here is a summary of the options to rzip.

        -0            fastest (worst) compression
        -6            default compression
        -9            slowest (best) compression
        -d            decompress
        -o filename   specify the output file name
        -S suffix     specify compressed suffix (default '.rz')
        -f            force overwrite of any existing files
        -k            keep existing files
        -P            show compression progress
        -V            show version

OPTIONS

       -h     Print an options summary page

       -V     Print the rzip version number

       -0..9  Set the compression level from 0 to 9. The default is to  use  level  6,  which  is  a  reasonable
              compromise  between  speed  and compression. The compression level is also strongly related to how
              much memory rzip uses, so if you are running rzip on a machine with limited amounts of memory then
              you will probably want to choose a smaller level.

       -d     Decompress. If this option is not used then rzip looks at the name used to launch the program.  If
              it contains the string 'runzip' then the -d option is automatically set.

       -o     Set  the  output file name. If this option is not set then the output file name is chosen based on
              the input name and the suffix. The -o option cannot  be  used  if  more  than  one  file  name  is
              specified on the command line.

       -S     Set the compression suffix. The default is '.rz'.

       -f     If  this  option is not specified then rzip will not overwrite any existing files. If you set this
              option then rzip will silently overwrite any files as needed.

       -k     If this option is not specified then rzip will delete the source file after successful compression
              or decompression. When this option is specified then the source files are not deleted.

       -P     If this option is specified then rzip will show the percentage progress while compressing.

INSTALLATION

       Just install rzip in your search path.

COMPRESSION ALGORITHM

       rzip operates in two stages. The first stage finds and encodes  large  chunks  of  duplicated  data  over
       potentially very long distances (up to nearly a gigabyte) in the input file. The second stage is to use a
       standard compression algorithm (bzip2) to compress the output of the first stage.

       The  key  difference  between  rzip  and  other  well known compression algorithms is its ability to take
       advantage of very long distance redundancy. The well known deflate algorithm used in gzip uses a  maximum
       history  buffer  of  32k.  The  block  sorting algorithm used in bzip2 is limited to 900k of history. The
       history buffer in rzip can be up to 900MB long, several orders of magnitude larger than gzip or bzip2.

       It is quite common these days to need to compress files that  contain  long  distance  redundancies.  For
       example,  when compressing a set of home directories several users might have copies of the same file, or
       of quite similar files. It is also common to have a single file that  contains  large  duplicated  chunks
       over  long  distances,  such  as pdf files containing repeated copies of the same image. Most compression
       programs won't be able to take advantage of  this  redundancy,  and  thus  might  achieve  a  much  lower
       compression ratio than rzip can achieve.

HISTORY

       The  ideas  behind rzip were first implemented in 1998 while I was working on rsync. That version was too
       slow to be practical, and was replaced by this version in 2003.

BUGS

       Unlike most Unix compression programs, rzip cannot compress or decompress to or from  standard  input  or
       standard output. This is due to the nature of the algorithm that rzip uses and cannot easily be fixed.

CREDITS

       Thanks to the following people for their contributions to rzip

       o      Paul Russell for many suggestions and the debian packaging

       o      The authors of bzlib for an excellent library

AUTHOR

       rzip was written by Andrew Tridgell http://samba.org/~tridge/

       If you wish to report a problem or make a suggestion then please email bugs-rzip@tridgell.net

       rzip is released under the GNU General Public License version 2 or later. Please see the file COPYING for
       license details.

                                                  October 2003                                           rzip(1)