Regular Expressions

Use either of these to formulate your regex expression. Both are Open Source.

Regexr Regex101

	Description
^	Matches the beginning of line
$	Matches the end of line
.	Mathes any character
\s	Matches whitespace; equivalent to [\t\n\r\f\v]
\S	Matches any NON-Whitespace; equivalent to [^\t\n\r\f\v]
*	Zero or more time; Repeats a character
*?	Zero or more times; NON-GREEDY; Repeats a character
+	One or More times; Repeats a character
+?	One or More times; NON-GREEDY; Repeats a character
[aeiou]	Matches a single character in the listed set
[^XYZ]	Matches a single character NOT in the listed set
[a-z0-9]	A set of character or an include range
(	Indicates where the string extraction starts
)	Indicates where the string extraction ends
a\|b	matches either a or b, a and b are string matching pattern
\	Escape character for special characters (\t, \n, \b)
\b	Matches word boundary
\d	Matches single digit; equivalent to [0-9]
\w	Alphanumeric character; [a-zA-Z0-9_]
\W	NON-Alphanumeric character; [^a-zA-Z0-9_]
?	Matches zero or One occurances
{n}	Exactly n repetitions, n>=0
{n,}	Atleast n repeatitions
{,n}	Atmost n repeatitions
{m,n}	Atleast m times and atmost n repeatitions

Regex Lookaround

Regex Lookaround

• Look ahead positive (?=)

  A(?=B) find expression A where expression B follows)

• Look ahead negative (?!)

  A(?!B) find expression A where expression B does not follow

• Look behind positive (?<=)

  (?<=B)A find expression A where expression B precesed

• Look behind negative (?<!)

  (?<!B)A find expression A where expression B does not precede