Lunzip

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Introduction

Lunzip is a decompressor for lzip files. It is written in C and its small size makes it well suited for embedded devices or software installers that need to decompress files but do not need compression capabilities. Lunzip is fully compatible with lzip-1.4 or newer.

The lzip file format is designed for long-term data archiving. It is clean, provides very safe 4 factor integrity checking, and is backed by the recovery capabilities of lziprecover.

Lunzip uses the same well-defined exit status values used by lzip and bzip2, which makes it safer than decompressors returning ambiguous warning values (like gunzip) when it is used as a back end for tar or zutils.

Lunzip provides a "low memory" mode able to decompress any file using as little memory as 50 kB, irrespective of the dictionary size used to compress the file. To activate it, specify the size of the output buffer with the "--buffer-size" option and lunzip will use the decompressed file as dictionary for distances beyond the buffer size. Of course, the smaller the output buffer size used in relation to the dictionary size, the more accesses to disk are needed and the slower the decompression is. This "low memory" mode only works when decompressing to a regular file and is intended for systems without enough memory (RAM + swap) to keep the whole dictionary at once. It has been tested on a laptop with a 486 processor and 4MiB of RAM.

The amount of memory required by lunzip to decompress a file is about 46 kB larger than the dictionary size used to compress that file, unless the "--buffer-size" option is specified.

Decompressing a file is much like copying or moving it; therefore lunzip preserves the access and modification dates, permissions, and, when possible, ownership of the file just as "cp -p" does. (If the user ID or the group ID can't be duplicated, the file permission bits S_ISUID and S_ISGID are cleared).

Lunzip is able to read from some types of non regular files if the "--stdout" option is specified.

If no file names are specified, lunzip decompresses from standard input to standard output. In this case, lunzip will decline to read compressed input from a terminal.

Lunzip 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.

Learn more about lzip in the Lzip Home Page.

Documentation

Lunzip only includes a man page and a README file. For information about the lzip file format see the online manual of lzip below.

The manual is available in the info system of the GNU Operating System. Use info to access the top level info page. Use info lzip to access the lzip section directly.

An online manual for lzip can be found here.

Download

The latest released version of lunzip can be found here. You may also subscribe to Freecode and receive an email every time a new version is released.

How to Get Help

For general discussion of bugs in lunzip 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 lunzip" 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.

How to Help

To contact the author, either to report a bug or to contribute fixes or improvements, send mail to lzip-bug@nongnu.org. Please send messages as plain text. If posting patches they should be in unified diff format against the latest version. They should include a text description.

See also the lzip project page at Savannah.

Licensing

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

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Copyright © 2014 Antonio Diaz Diaz
Lzip logo Copyright © 2013 Sonia Diaz Pacheco

You are free to copy, modify and distribute all or part of this article without limitation.

Updated: 2014/04/16