1rzip(1)                                                                rzip(1)
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NAME

6       rzip - a large-file compression program
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SYNOPSIS

9       rzip [OPTIONS] <files...>
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DESCRIPTION

12       rzip  is a file compression program designed to do particularly well on
13       very large files containing long distance redundency.
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OPTIONS SUMMARY

16       Here is a summary of the options to rzip.
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20        -0            fastest (worst) compression
21        -6            default compression
22        -9            slowest (best) compression
23        -d            decompress
24        -o filename   specify the output file name
25        -S suffix     specify compressed suffix (default '.rz')
26        -f            force overwrite of any existing files
27        -k            keep existing files
28        -P            show compression progress
29        -V            show version
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OPTIONS

35       -h     Print an options summary page
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37       -V     Print the rzip version number
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39       -0..9  Set the compression level from 0 to 9. The  default  is  to  use
40              level 6, which is a reasonable compromise between speed and com‐
41              pression. The compression level is also strongly related to  how
42              much  memory  rzip uses, so if you are running rzip on a machine
43              with limited amounts of memory then you will  probably  want  to
44              choose a smaller level.
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46       -d     Decompress.  If  this  option is not used then rzip looks at the
47              name used to launch the program. If it contains the string 'run‐
48              zip' then the -d option is automatically set.
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50       -o     Set  the  output  file  name. If this option is not set then the
51              output file name is chosen based on the input name and the  suf‐
52              fix.  The -o option cannot be used if more than one file name is
53              specified on the command line.
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55       -S     Set the compression suffix. The default is '.rz'.
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57       -f     If this option is not specified then rzip will not overwrite any
58              existing  files.  If you set this option then rzip will silently
59              overwrite any files as needed.
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61       -k     If this option is not specified then rzip will delete the source
62              file  after  successful  compression or decompression. When this
63              option is specified then the source files are not deleted.
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65       -P     If this option is specified then rzip will show  the  percentage
66              progress while compressing.
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INSTALLATION

69       Just install rzip in your search path.
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COMPRESSION ALGORITHM

72       rzip  operates  in  two stages. The first stage finds and encodes large
73       chunks of duplicated data over potentially very long distances  (up  to
74       nearly  a  gigabyte)  in  the  input file. The second stage is to use a
75       standard compression algorithm (bzip2) to compress the  output  of  the
76       first stage.
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78       The  key difference between rzip and other well known compression algo‐
79       rithms is its ability to take advantage of very  long  distance  redun‐
80       dency.  The  well  known  deflate algorithm used in gzip uses a maximum
81       history buffer of 32k. The block sorting algorithm  used  in  bzip2  is
82       limited  to  900k  of  history. The history buffer in rzip can be up to
83       900MB long, several orders of magnitude larger than gzip or bzip2.
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85       It is quite common these days to need to compress  files  that  contain
86       long distance redundancies. For example, when compressing a set of home
87       directories several users might have copies of the  same  file,  or  of
88       quite  similar files. It is also common to have a single file that con‐
89       tains large duplicated chunks over long distances, such  as  pdf  files
90       containing repeated copies of the same image. Most compression programs
91       won't be able to take advantage of  this  redundency,  and  thus  might
92       achieve a much lower compression ratio than rzip can achieve.
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HISTORY

95       The  ideas behind rzip were first implemented in 1998 while I was work‐
96       ing on rsync. That version was  too  slow  to  be  practical,  and  was
97       replaced by this version in 2003.
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BUGS

100       Unlike  most  Unix compression programs, rzip cannot compress or decom‐
101       press to or from standard input or standard output. This is due to  the
102       nature of the algorithm that rzip uses and cannot easily be fixed.
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CREDITS

105       Thanks to the following people for their contributions to rzip
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107       o      Paul Russell for many suggestions and the debian packaging
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109       o      The authors of bzlib for an excellent library
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AUTHOR

112       rzip was written by Andrew Tridgell http://samba.org/~tridge/
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114       If  you wish to report a problem or make a suggestion then please email
115       bugs-rzip@tridgell.net
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117       rzip is released under the GNU General  Public  License  version  2  or
118       later. Please see the file COPYING for license details.
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122                                 October 2003                          rzip(1)
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