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)