Regexp - Look-around group (Assertion) - ( Lookahead | Lookbehind )

> Procedural Languages > Multilingual Regular Expression Syntax (Pattern)

1 - About

Look-around are non-capturing group that implements an assertion pattern.

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3 - List

If you don't find your pattern below, question mark has other functionality in regular expression. See them all at Regular Expression - Question Mark (?)

Assertion
(?=X) X, positive lookahead (via zero-width)
(?!X) X, negative lookahead (via zero-width)
(?<=X) X, positive lookbehind (via zero-width)
(?<!X) X, negative lookbehind (via zero-width)

where X is a sub-regular expression