Gunzip

Gzip

Original author(s)	Jean-loup Gailly Mark Adler
Developer(s)	GNU Project
Initial release	31 October 1992; 24 years ago (1992-10-31)
Stable release	1.8 (GNU Gzip) / 26 April 2016; 11 months ago (2016-04-26)
Repository	git.savannah.gnu.org/cgit/gzip.git
Written in	C
Operating system	Unix-like
Type	Data compression
License	GNU GPLv3
Website	www.gnu.org/software/gzip/

gzip is a file format and a software application used for file compression and decompression. The program was created by Jean-loup Gailly and Mark Adler as a free software replacement for the compress program used in early Unix systems, and intended for use by GNU (the "g" is from "GNU"). Version 0.1 was first publicly released on 31 October 1992, and version 1.0 followed in February 1993.

gzip is based on the DEFLATE algorithm, which is a combination of LZ77 and Huffman coding. DEFLATE was intended as a replacement for LZW and other patent-encumbered data compression algorithms which, at the time, limited the usability of compress and other popular archivers.

"gzip" is often also used to refer to the gzip file format, which is:

Although its file format also allows for multiple such streams to be concatenated (zipped files are simply decompressed concatenated as if they were originally one file), gzip is normally used to compress just single files. Compressed archives are typically created by assembling collections of files into a single tar archive, and then compressing that archive with gzip. The final .tar.gz or .tgz file is usually called a tarball.

gzip is not to be confused with the ZIP archive format, which also uses DEFLATE. The ZIP format can hold collections of files without an external archiver, but is less compact than compressed tarballs holding the same data, because it compresses files individually and cannot take advantage of redundancy between files (solid compression).