The eval command allows you to run the contents of variables as commands and can be very useful -- especially in scripts.

The everlastingly useful grep command can change its character with the flip of a switch to help you find things.

How to find files in Linux with grep: 10 examples (free PDF) The grep command is a handy, reliable tool for searching for files or information.

Linux/BSD command line wizardry: Learn to think in sed, awk, and grep "Do people really write these long, convoluted commands?" In a word: yes.

After a while you start both putting commands into scripts and typing one-off multi-line small programs just on the command line.

With regex and grep, you can search for patterns in text files with either simple or very complex patterns. Also: The first 5 Linux commands every new user should learn ...

After jumping into the Ubuntu command line yesterday, today I decided to dive a little deeper and explore the 'man' and 'grep' commands more closely.