Regular Expression Validator
Regex is a popular pattern patching expression used in popular scripting languages like Sed, Awk, PHP and Perl to match strings. Use our online tool to test, debug and validate regular expressions for easier coding practices.
What is the regular expression?
A regular expression is a pattern used in a scripting languages such as the Sed, Awk, PHP, Perl, Bash and other programming languages to match subject string. It is used to search a string (or text) to match all occurances of a pattern, and allows it to act on it (i.e. replace with another string).
Patterns
A regular expression uses a pattern to match a string. There are literal characters which matches exact character, and wildcard characters that matches a variety of characters. Also, there are symbols that match number of occurances (?, + and *). To give you a flavor of how regular expression works, here are some concepts used to match a text.
| Meta Character |
Operation |
Example |
Description |
| | |
Or |
apple|orange|pear |
Matches apple, orange, or pear |
| () |
Group |
gr(a|e)y |
Matches grey or gray |
| . |
Any char |
a.c |
Matches abc, adc, aMc |
| ? |
0 or 1 occurance |
colou?r |
Matches color or colour |
| * |
0 or more occurance |
xyz* |
Matches xy, xyz, xyzz |
| + |
1 or more occurance |
xyz+ |
Matches xyz, xyzz, xyzzz |
| - |
Range with bracket |
[a-z] |
Matches a, b, through z |
| [] |
Or 1 character |
[abc] |
Matches a, b or c |
| [^ ] |
Not contained |
[abc] |
Matches any char but a, b or c |
| ^ |
Beginning of string |
^abc |
Matches starting with abc |
| $ |
End of string |
xyz$ |
Matches string ending xyz |
| \t |
Tab |
\t |
Matches tab |
| \n |
New Line |
\n |
Matches new line |
| \n, n=1..9 |
Match nth item |
(abc|xyz)\1 |
Matches abcabc, abcxyz |
| {n}, n=1..9 |
match n times |
a{3} |
Matches aaa |
