Regex 101

Online resources

Online resources for regular expressions:

Website	Description
https://regex101.com/	Online testing of regex, supporting different regex types / languages. Detailed explanation of the different regex parts.

Regex basic cheatsheet

keyword	Description
a	Matches the character a.
a|b	Matches either the character a or b.
a?	Matches zero or one a.
a*	Matches zero or more a.
a+	Matches one or more a, as many times as possible, giving back as needed (greedy).
a+?	Matches one or more a, as few times as possible, expanding as needed (lazy).
a{5}	Matches exactly 5 consecutive a.
a{5-10}	Matches between 5 to 10 (inclusive) consecutive a.
a{5,}	Matches 5 or more consecutive a.
.	Matches any single character.
\s	Matches any single space, tab or newline character.
\S	Matches any single character that is not a space, tab or newline.
\d [0-9]	Matches any single digit character.
\D [^0-9]	Matches any single character that is not a digit.
\w [a-zA-Z0-9_]	Matches any single letter, digit, or underscore.
\W [^a-zA-Z0-9_]	Matches any single any single character that is not a letter, digit, or underscore.
^	Matches the start of the string.
^abc	Matches a string starting by abc.
$	Matches the end of the string.
xyz$	Matches a string ending by xyz.
[xyz]	Matches a single character among x, y, or z.
[^xyz]	Matches any character except for x, y or z.
[a-z]	Matches a single character in the range a to z.
[a-zA-Z]	Matches a single character in the range a to z or A to Z.
[^a-z]	Matches any character except those in the a to z range.

Regex examples

Regex	Description
((25[0-5]|2[0-4][0-9]|1?[0-9][0-9]?)\\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)(:[1-65535]\D)?	Matches an IPv4 address, with an eventual port number.