Bash scripting (shell scripting using bash) is one of the most critical skills a hacker can cultivate. Everybody and his brother (including me, Glenn) has written bash scripting guides and tutorials, but few of them go as in-depth as this one.
I’ll be listing other bash tutorial sites here at School for Hackers, and I hope eventually to put together a course and cert in bash scripting for hackers. Drop me a line if you’re interested in working on that project. In the mean time, see this: