Chances are you’ve come across archived or compressed files and downloaded them. To interact with them through the command line, the Linux shell comes standard with many compression / decompression and archive / extraction commands.

Let’s first talk about the compression commands which reduce file sizes and differ mainly by the algorithms behind them. Three popular compression commands are:

• gzip: retains the original file’s ownership modes, access, and modification timestamps. Compressed files have the .gz extension.
• bzip2: compressed files have the .bz2 extension.
• xz: compressed files have the .xz extension.

The syntax to compress a file using one of these compression utilities is:

<compression_utility> [options] <file_name>

For example, the command gzip hello.txt will result in a compressed file named hello.txt.gz and delete the original file. Adding the -k option will retain the original file.

Multiple files can be compressed by adding all of their names as arguments or by using the wildcard symbol (*). For example:

bzip2 poem.txt riddle.txt

will result in two compressed files: poem.txt.bz2 and riddle.txt.bz2 whereas

xz *.txt

would compress all files in the current directory with the .txt extension.

The gzip command has the ability to compress all files in a directory using the -r option and providing the path to a directory.

Files can be decompressed using the -d option.

Note: For more information and options, you can refer to the manual or info pages for these commands or use the --help option for each command.

In the next exercise, we will learn about the popular archive utilities available on the Linux shell: zip and tar.