Bash Shell Snippets

file extension
http://liquidat.wordpress.com/2007/09/29/short-tip-get-file-extension-in-shell-script/

find files for a do loop
http://www.davidpashley.com/articles/writing-robust-shell-scripts.html

parameter substitution – undefinded parameters
http://tldp.org/LDP/abs/html/parameter-substitution.html