Listing, Reading, & Decompressing GZip (GNU zip) Files

For a little background on GNU zip. GNU zip is a file format and application commonly used for compression and decompression. This is generally the default compression method for logging archives in GNU based Linux distributions. The initial release of GNU zip was October 31, 1992 and created by Jean-loup Gailly and Mark Adler.

Below are some ways to get help with GNU zip. The first one is to view the man page for gzip.

man gzip

This command shows the usage for gzip.

gzip -h

These are some notes for decompressing/opening Gzip files. I generally utilize these commands mostly for decompressing old log files stored in the /var/log/ directory. But, this can also be used for other scenarios.

I’ll provide some commands for listing items within the compressed files because it’s generally useful to see the files compressed in these .gz files.

List the files within the Gzip file.

gzip -l /path/to/file.gz

If you were to run this command on a file like /var/log/auth.log.2.gz this would be the output we could expect.

         compressed        uncompressed  ratio uncompressed_name
              13572              120446  88.7% auth.log.2

This command will take the standard output of the file and display it in the terminal.

gunzip -c /path/to/file.gz

The following command will do the same.

zcat /path/to/file.gz

Decompress the files and delete the Gzip file.

gzip -d /path/to/file.gz

Decompress the files from the archive and keep the existing Gzip file.

gzip -dk /path/to/file.gz

The gunzip command will decompress .gz files as well. This will effectively decompress the file. Then it will vomit the file. While in the reverse. It will compress the file and add the .gz extension to it.

gunzip /path/to/file.gz