![[lzip logo]](lzip.png)
Lzip replaces every file given in the command line with a compressed version of itself, with the name "original_name.lz". Each compressed file has the same modification date, permissions, and, when possible, ownership as the corresponding original, so that these properties can be correctly restored at decompression time. Lzip is able to read from some types of non regular files if the "--stdout" option is specified.
If no file names are specified, lzip compresses (or decompresses) from standard input to standard output. In this case, lzip will decline to write compressed output to a terminal, as this would be entirely incomprehensible and therefore pointless.
Lzip will correctly decompress a file which is the concatenation of two or more compressed files. The result is the concatenation of the corresponding uncompressed files. Integrity testing of concatenated compressed files is also supported.
Lzip can produce multimember files and safely recover, with lziprecover, the undamaged members in case of file damage. Lzip can also split the compressed output in volumes of a given size, even when reading from standard input. This allows the direct creation of multivolume compressed tar archives.
Lzip will automatically use the smallest possible dictionary size for each member without exceeding the given limit. It is important to appreciate that the decompression memory requirement is affected at compression time by the choice of dictionary size limit.
As a self-check for your protection, lzip stores in the member trailer the 32-bit CRC of the original data and the size of the original data, to make sure that the decompressed version of the data is identical to the original. This guards against corruption of the compressed data, and against undetected bugs in lzip (hopefully very unlikely). The chances of data corruption going undetected are microscopic, less than one chance in 4000 million for each member processed. Be aware, though, that the check occurs upon decompression, so it can only tell you that something is wrong. It can't help you recover the original uncompressed data.
The LZMA (Lempel-Ziv-Markov chain-Algorithm) algorithm was designed by Igor Pavlov. The high compression of LZMA comes from combining two basic, well-proven compression ideas: sliding dictionaries (LZ77/78) and markov models (the thing used by every compression algorithm that uses a range encoder or similar order-0 entropy coder as its last stage) with segregation of contexts according to what the bits are used for.
If you need a library able to compress/decompress lzip data streams, see Lzlib.
For general discussion of bugs in lzip the mailing list lzip-bug@nongnu.org is the most appropriate forum. Please send messages as plain text. Please do not send messages encoded as HTML nor encoded as base64 MIME nor included as multiple formats. Please include a descriptive subject line. If all of the subject are "bug in lzip" it is impossible to differentiate them.
An archive of the bug report mailing list is available at http://lists.nongnu.org/mailman/listinfo/lzip-bug.
See also the lzip project page at Savannah.
You are free to copy, modify and distribute all or part of this article without limitation.
Updated: 2009/05/02