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rzip is a compression program, similar in functionality to gzip or bzip2.




rzip is a compression program, similar in functionality to bzip2 or gzip, but able to take advantage long distance redundencies in files, which can sometimes allow rzip to produce much better compression ratios than other programs.

The original idea behind rzip is described in my PhD thesis (see http://samba.org/~tridge/), but the implementation in this version is considerably improved from the original implementation.

The new version is much faster and also produces a better compression ratio.


The principal advantage of rzip is that it has an effective history buffer of 900 Mbyte. This means it can find matching pieces of the input file over huge distances compared to other commonly used compression programs. The gzip program by comparison uses a history buffer of 32 kbyte and bzip2 uses a history buffer of 900 kbyte.

The second advantage of rzip over bzip2 is that it is usually faster. This may seem surprising at first given that rzip uses the bzip2 library as a backend (for handling the short-range compression), but it makes sense when you realise that rzip has usually reduced the data a fair bit before handing it to bzip2, so bzip2 has to do less work.


rzip is not for everyone! The two biggest disadvantages are that you can't pipeline rzip (so it can't read from standard input or write to standard output), and that it uses lots of memory. A typical compression run on a large file might use a couple of hundred MB of ram. If you have ram to burn and want the best possible compression rate then rzip is probably for you, otherwise stick with bzip2 or gzip.

What's New in This Release:

Added -L compression level option
minor portability fixes
fixed a bug that could cause some files to not be able to be uncompressed
Last updated on February 14th, 2006

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