Regex 101
Online resources
Online resources for regular expressions:
https://regex101.com/
Online testing of regex, supporting different regex types / languages. Detailed explanation of the different regex parts.
Regex basic cheatsheet
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
((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.
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