B.5 Atomic Zero-Width Assertions
The following table describes the atomic zero-width assertions. The metacharacters described in the following table do not cause the engine to advance through the string or consume characters. They simply cause a match to succeed or fail depending on the current position in the string.
Table B.6 | List of Atomic Zero-Width Assertions |
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^
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Specifies that the match must occur at the beginning of the document or the beginning of the line.
For example, ^#region returns only those occurrences of the character string #region that occur at the beginning of a line.
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$
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Specifies that the match must occur at the end of the string, before \n at the end of the string, or at the end of the line.
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\A
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Specifies that the match must occur at the beginning of the document.
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\z
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Specifies that the match must occur at the end of the document.
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\b
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Specifies that the match must occur on a boundary between \w (alphanumeric) and \W (nonalphanumeric) characters.
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\B
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Specifies that the match must not occur on a \b boundary.
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