Regular Expressions Syntax summary

Items to match a single character
Meta characters		Matches
.	Dot	Matches any one character
[….]	Character class	Matches any one character listed
[^….]	Negated character class	Matches any one character not listed
\char	Escaped character	Matches literal character
Items appended to provide “Counting” : The Quantifiers
?	question	One allowed but it is optional
*	star	Any number allowed but all are optional
+	Plus	At least one is required; additional are optional
{min, max}	Specified range	Min required , Max allowed
Items that match a position
^	Caret	Matches the position at the start of the line
$	Dollar	Matches the position at the end of the line
\<	Word boundary	Matches the position at the start of the word
\>	Word boundary	Matches the position at the end of the word
|	Alternation	Matches either expression it separates
( )	Parentheses	Limits the scope of alternation, provides the grouping for quantifier and captures for back references
\1 \2	Back references	Matches the text previously match within first , second etc.
\t	Tab character
\n	Newline character
\r	Carriage return
\s		Matches any whitespace
\S		Any thing not \s
\w		Matches any word
\W		Matches non word [^a-zA-Z0-9_]
\d		Matches any numeric digit [0-9]
\D		Any thing not \d
(?<=…)	Look behind	Successful if can match to the left
(?<!...)	Negative look behind	Successful if can not match to the left
(?=…..)	Look ahead	Success full if can match to the right
(?!....)	Negative look ahead	Successful if can not match to the right