The .gz file extension are created using Gzip program which reduces the size of the named files using Lempel-Ziv coding (LZ77). gunzip / gzip is software application used for file compression. gzip is short for GNU zip; the program is a free software replacement for the compress program used in early Unix systems.

Each file is replaced by one with the extension .gz, while keeping the same ownership modes, access and modification times.

To expand i.e. to Unpacking or uncompressing gz files you need to use gunzip program Or gzip -d or zcat program:

Using gunzip command:

$ gunzip file.gz
$ ls file

Using gzip -d command:

$ gzip -d file.gz
$ ls file

If file extension is tar.gz, type the command:

$ tar -zxvf file.tar.gz

Please note that gunzip can currently decompress files created by gzip, zip, compress, compress -H or pack programs.