If you are using fedora or CentOS as a work station or on a VPS you can enhance your bash auto-completion (That appears when you press TAB key). To do this print the following command as root:

yum install bash-completion

Then open a new bash shell (new terminal if you are using a GUI or logout then login again if you are using ssh or a terminal). This simple package adds powerful completion to your commands, here is a list of what you may expect from this package:

• Auto-completion for yum commands and packages. Try to write yum in then press tab it will complete it to yum install then try to write a part from a package name and see the magic.
• Completion for command args (arguments that starts with – or –).
• Smart selection of file and folder types with commands like (cd, tar, gunzip, unzip, ….)
• Completion for commands options (just like yum). This works with version control command line tools.
• And a lot more ….

Mercurial option auto complete in Fedora

For Ubuntu users this addition is already installed with default installation.