RegEx

Quantifiers

*	0 or more
+	1 or more
?	0 or 1
{3}	Exactly 3
{3,}	3 or more
{3,5}	3, 4 or 5

Groups and Ranges

.	Any character except new line
(a{|}b)	a or b
(...)	Group
(?:...)	Passive Group
{[abc}	Range (a or b or c)
{[^abc}	Not a or b or c
{[a-q}	Letter between a and q
{[A-Q}	Upper case between A and Q
{[0-7}	Digit between 0 and 7
\n	Digit between 0 and 7

Anchors

^ or \A	Start of string
$ or \Z	End of string
\b	Word boundary
\B	Not word boundary
\<	Start of word
\>	End of word

POSIX

{[:upper:}	Upper case letters
{[:lower:}	Lower case letters
{[:alpha:}	All letters
{[:alnum:}	Digits and letters
{[:digit:}	Digits
{[:punct:}	Punctuation
{[:blank:}	Space and tab
{[:space:}	Blank characters
{[:word:}	Digits, letters and underscore

Character Classes

\c	Control character
\s	White space
\S	Not white space
\d	Digit
\D	Not digit
\w	Word
\W	Not word

Special Characters

\	Escape Character
\n	New line
\r	Carriage return
\t	Tab
\v	Vertical tab
\f	Form feed