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REGEX

Anchors


Anchors

Anchors, also known as atomic zero-width assertions, cause a match to succeed or fail depending on the current position in the string.

It is important to note that anchors do not cause the regular expression engine to advance the current position in the string or consume characters.

Start of Line/String ( ^ , \A )

Specifies that the match must occur at the beginning of the text being searched. In multiline mode, ^ matches after any newline character (i.e. beginning of the line).

End of Line/String ( $, \Z, \z )

Specifies that the match must occur at the end of the text being searched. In multiline mode, $ matches before after any newline character (i.e. end of the line).

Start of Match ( \G )

Specifies that the match must occur where the previous match ended.

Word Boundary ( \b, \B, \<, \> )

The \b anchor specifies that the match must occur where a word character is next to a non-word character, whereas \B specifies a not-word-boundary location.

Some regular expression engines support \< and \> for start-of-word and end-of-word boundaries.

Lookahead ( (?=...), (?!...) )

Specifies that the match must occur at a location where the specified subpattern would match (lookahead) or would not match (negative lookahead).

Lookbehind ( (?<=...), (?<!...) )

Specifies that the match must occur at a location where the specified subpattern would have finished matching (lookbehind) or would not have finished matching (negative lookbehind).



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