Open ZIP File

GZ File

GZ file format was introduced by Jean-loup Gailly and Mark Adler in 1992. They developed gzip utility as a replacement of an old Unix utility named “compress”. In comparison with “compress” gzip provided superior compression and was implemented in a way to avoid copyright infringement. “compress” utility used LZW algorithm which while being effective was covered under patents from Unisys and IBM. Until these patents expired there could have been legal consequences with using compression utilities based on LZW algorithm and that is one of the main reasons why gzip utility and GZ format came into existence.

Gzip utility uses DEFLATE algorithm to compress and decompress data. DEFLATE algorithm typically compresses more effectively than LZW while taking more memory and CPU resources.

Gzip is developed in such a way that it can only compress or decompress a single file. To work with multiple files, it needs to work together with TAR utility. TAR utility can combine several files from different locations in a single combined file called TAR archive. TAR could be used in combination with gzip in such a way that every file is compressed by gzip before being added to TAR archive. The resulting file gets .tar.gz file extension. Same happens during unarchiving. TAR removes files one by one from TAR archive and applies gunzip decompression utility to each file.

Below are commands which could be used for TAR/gzip compression and decompression

tar -zcvf target-archive-name.tar.gz source-files

tar -zxvf source-archive-name.tar.gz

Below is a description of options used above:
-c create archive file
-x extract archive file
-z all files should be compressed by gzip
-v show progress of compression
-f output result to a specified file

A popular alternative to gzip is bzip2. This a newer file compression utility which uses more advanced LZMA and Burrows-Wheeler algorithms and can also work in tandem with TAR while producing tar.bz2 files.