.TH "rzip64" "1" "December 2010" "" "" 
.SH "NAME" 
rzip64 \- a large-file compression program
.SH "SYNOPSIS" 
.PP 
rzip64 [OPTIONS] <files\&.\&.\&.>
.PP 
.SH "DESCRIPTION" 
.PP 
rzip64 is a file compression program designed for very large files\&.
When processing large chunks of input data it takes advantage of repetitiv appearing 
byte patterns over long distances\&.
.PP 
rzip64 can utilize multiple CPU cores\&. rzip64 can also be interrupted at any time
and be restarted later\&. 
.PP 
.SH "OPTIONS SUMMARY" 
.PP 
Here is a summary of the options to rzip64\&.

.nf 
 

 -0            fastest (worst) compression
 -6            default compression
 -9            slowest (best) compression
 -d            decompress
 -f            force overwrite of any existing files
 -G            use slices (stop-and-go mode)
 -h            print this help text
 -j            use n cores in parallel
 -k            keep existing files
 -o filename   specify the output file name
 -P            show compression progress
 -S suffix     specify compressed suffix (default \e&\'\e&\&.rz\e&\')
 -V            show version

.fi 
 

.PP 
.SH "OPTIONS" 
.PP 
.IP "\fB-0\&.\&.9\fP" 
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\&.
.IP "\fB-d\fP" 
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\&.
.IP "\fB-f\fP" 
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\&.
.IP "\fB-G\fP" 
This option enables
the stop-and-go mode of rzip64\&. If this option is used rzip64 may be
interrupted via signal (say kill -15) at any time\&. Wenn rzip64 is restarted
later it will proceed compressing the file\&. -G always implies -9\&.
.IP "\fB-h\fP" 
Print an options summary page
.IP "\fB-j n\fP" 
Use n cpu cores in parallel\&. Using more than a single
core autoselects -G, too\&.
.IP "\fB-k\fP" 
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\&.
.IP "\fB-o\fP" 
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\&.
.IP "\fB-P\fP" 
If this option is specified then rzip will show the
percentage progress while compressing\&.
.IP "\fB-S\fP" 
Set the compression suffix\&. The default is \'\&.rz\'\&. 
.IP "\fB-V\fP" 
Print the rzip64 version number
.PP 
.SH "INSTALLATION" 
.PP 
Just install rzip in your search path\&.
.PP 
.SH "STOP-AND-GO MODE" 
.PP 
Compressing a large file takes time an imposes a considerable load on
the machine\&. It is therefore desireable to run compression tasks only at 
times where no users are working on the machine\&.
.PP 
rzip64 can therefore be interrupted at any time by a simple kill command\&.
When rzip64 is restarted later it will continue the compression task until
the job is completed\&. One may even change the number of cores when
restarting\&.
.PP 
.SH "HISTORY" 
.PP 
The ideas behind rzip64 were first implemented in 1998 during the work 
on rsync\&. That version was too slow to be practical, and was
replaced by version 2\&.1 in 2003\&.
.PP 
The stop-and-go option was added in 09/2010 (version 2\&.2)\&.
.PP 
Multicore support was added in 12/2010\&. The version number was advanced to
3\&.0 since rzip64 with multiple treads requires a considerable amount of
memory address space that can typically be provided by 64 bit environments only\&.
It is not a matter of physical RAM modules but of virtual address space\&. Each 
cpu core requires about 900 MByte address space\&.
.PP 
One can still compile an run rzip64 in 32 bit environments (while using only a
small number of cpu cores) but that is no longer recommended\&. 
.PP 
.SH "COMPATIBILITY" 
.PP 
The file format for rzip64 is fully compatible to rzip 2\&.1 and 2\&.2 \&.
.PP 
.SH "NOTE" 
.PP 
Unlike most Unix compression programs, rzip64 cannot compress or
decompress to or from standard input or standard output\&. That can possibly be 
changed but appears to make not much sense when -G is in use\&. 
.PP 
.SH "RESSOURCES" 
.PP 
If you wish to report a problem or make a suggestion then please email
rzip64@GHSi\&.eu \&.
.PP 
Source code and binary packages are available at rzip64\&.GHSi\&.eu \&.
.PP 
.SH "AUTHOR" 
.PP 
Different people have put work in the development of rzip64\&.
Our thanks include
.IP o 
Andrew Tridgell for the first implementation of rzip
.IP o 
The authors of bzlib for an excellent library
.IP o 
Paul Russell for many suggestions and the debian packaging
.IP o 
Kay Gorontzi for the stop-and-go and multicore extensions
.PP 
rzip64 is released under the GNU General Public License version 3 or
later\&. Please see the file COPYING for license details\&.
