Like all GNU/Linux and Unix operating systems Debian has a powerful command line interface, or CLI. Far from a thing of the past, it offers efficient, robust and complete control for beginners and experts alike.
https://gna.org/projects/mbfl - Marco's Bash Functions Library
http://linux.org.mt/article/terminal - Terminal
http://www.ssuet.edu.pk/~amkhan/Linuxbooks/Linux%20Shell%20Scripting%20Tutorial.pdf - Linux Shell Scripting Tutorial
http://www.tldp.org/LDP/abs/html - Advanced Bash-Scripting Guide
http://www.tldp.org/LDP/Bash-Beginners-Guide/html/index.html - Bash Guide for Beginners
http://linuxcommand.org/ - "...tired of changing your desktop themes. You keep seeing this "terminal" thing. Now what?"
http://web.archive.org - The history of unix shells