Regular Expression Quick Reference

.	Match single character except newline.
x*	Match zero or more x.
[xyz]	Match a character from x, y or z.
[^xyz]	Match any single character except x, y, or z.
[a-zA-Z0-9]	Match a character from a to z, A to Z, or 0 to 9 inclusive.
^x	Match x at beginning of the line.
x$	Match x at end of the line.
x\{2,4\}	Match 2 to 4 x inclusive.
x+	Match one or more x.
x?	Match zero or one x.
x|y	Match either x or y.
\	Escapes the special character e.g. \t => TAB, \n => newline.
()	Groups regular expressions e.g. (x|y)+.

Reference: UNIX Power Tools: sed & awk by Dale Dougherty