http://www.thegeekstuff.com/2010/07/bash-string-manipulation

http://www.thegeekstuff.com/2010/11/strings-command-examples/

http://www.thegeekstuff.com/2011/01/regular-expressions-in-grep-command/

tr, useful string tranformation tool - http://www.thegeekstuff.com/2012/12/linux-tr-command/
