
The following online guides are available:
AptGetHowto - using apt-get to install packages from the command line.
Commandline Repository Editing - managing software repositories through the command line.
grep Howto - grep is a powerful command line search tool.
find - locate files from the command line.
Commandline Howto - longer and more complete than this basic guide; still not finished, however.
Howto Readline - information on more advanced customization for the command line.
For more detailed tutorials on the Linux™ command line, please see:
http://ss64.com/bash/ - an A-Z index of the Bash™ command line for Linux™.
http://linuxcommand.org/ - basic BASH tutorials, including BASH scripting.
http://linuxsurvival.com/index.php - Java™-based tutorials.
http://rute.2038bug.com/index.html.gz - a massive online book about system administration — almost all from the command line.
http://www.commandlinefu.com/ - a place to record command line favorites and view others' gems as well.