1rzip(1) rzip(1)
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6 rzip - a large-file compression program
7
9 rzip [OPTIONS] <files...>
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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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16 Here is a summary of the options to rzip.
17 -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
30
35 -h Print an options summary page
36 -V Print the rzip version number
38 -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.
45 -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.
49 -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.
54 -S Set the compression suffix. The default is '.rz'.
56 -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.
60 -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.
64 -P If this option is specified then rzip will show the percentage
66 progress while compressing.
67
69 Just install rzip in your search path.
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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.
77 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.
84 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.
93
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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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.
103
105 Thanks to the following people for their contributions to rzip
106 o Paul Russell for many suggestions and the debian packaging
108 o The authors of bzlib for an excellent library
110
112 rzip was written by Andrew Tridgell http://samba.org/~tridge/
113 If you wish to report a problem or make a suggestion then please email
115 bugs-rzip@tridgell.net
116 rzip is released under the GNU General Public License version 2 or
118 later. Please see the file COPYING for license details.
119 October 2003 rzip(1)