Regular Expressions

Regular Expressions is an important part of development. Although it seems simple but to write complex regular expressions is very difficult task. Regular Expression are used to validate data against it and also used for pattern matching and for searching and replacing of strings.

I am providing a facility here by which you can validate expressions also.

Regular Expression:	Test String:

Result:


Below are the list of characters which are used in Regular Expressions for creating Regular Expressions.

Wildcard Character	Description
*	Zero or more occurrences of the previous character or sub-expression. For Example: PREV*included Matched: included PREVincluded Not Matched: PREVPREVincluded (Although Description says sub-expression could occur multiple time but actually it can occur only single time like in below example.) Second Example: a*included Matched: included aincluded aaincluded aaaincluded Not Matched: abincluded aacincluded aaabhdgincluded
+	One or more occurrences of the previous character or sub-expression. For Example: PREV+included Matched: PREVincluded Not Matched: included PREVPREVincluded (Although Description says sub-expression could occur multiple times but actually it can occur only single time like in below example.) Second Example: a+included Matched: aincluded aaincluded aaaincluded Not Matched: included aacincluded aaabhdgincluded
()	Groups a sub-expression that will be treated as a single element. For Example: (SingleElement)+ Matched: SingleElement SingleElementSingleElement SingleElementSingleElementSingleElement SingleElementSingleElementSingleElementSingleElement and many more like above.
|	Its same like OR operator which takes two operands and match any one operand or both. For Example: First|Second Matched: First Second Second Example: http|www|ftp Matched: http httpwww httpwwwftp httpftpwww
{}	Matches one character in a range of valid characters. For Example: [A-D] Matched: A ABCD AF B12 Not Matched: NF KJ 12 12 $#
[^]	Matches a character that isn’t in the given range. For Example: [^A-C] Matched: D D1 123abc abc and many more like above. Not Matched: A B C
.	Any character except newline means instead of dot (.) character you can use any character but you cannot find matches in multiple lines. For Example: .word Matched: aword bword Aword 1word #word and many more like above. Not Matched: word abword 12word AB12dvfword #$word Could not match in multiple lines.
\s	Any white-space character (such as a Tab or Space). For Example: Space Character Tab Character New Line Character Carriage Return Form Feed Character Vertical Tab Character
\S	Any non white-space character. For Example: Matched: Any alphanumeric or special character Not Matched: Space Character Tab Character New Line Character Carriage Return Form Feed Character Vertical Tab Character
\d	Any digit character. For Example: \d Matched: Match any character from 0-9 Not Matched: Any alphabetic character or special character.
\D	Any character that isn’t a digit. For Example: \D Matced: Match any alphabetic or special character. Not Matched: Any character from 0-9
\w	Any “word” character (letter, number, or underscore). For Example: \w Matched: A-Z, a-z, 0-9 or underscore Not Matched: Special characters except underscore.
\W	Any non word character. For Example: \W Matched: % $ # any other character which are not in Not Matched category below. Not Matched: A-Z, a-z, 0-9

Hope you have found the post useful. I am grateful for your positive feedback to improve.