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Help: Document how escape sequences work in a regex

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Our regex engine doesn't interpret `\`-escapes but CMake language escape
sequences may be used to pass literal whitespace characters to it.
This commit is contained in:
Brad King
2018-07-18 10:23:26 -04:00
parent 11d71e6cd0
commit 4b35dab891
1 changed files with 14 additions and 0 deletions
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Help/command/string.rst
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@@ -151,6 +151,20 @@ has lower precedence than concatenation. This means that the regular
expression ``^ab+d$`` matches ``abbd`` but not ``ababd``, and the regular expression ``^ab+d$`` matches ``abbd`` but not ``ababd``, and the regular
expression ``^(ab|cd)$`` matches ``ab`` but not ``abd``. expression ``^(ab|cd)$`` matches ``ab`` but not ``abd``.
Backslash (``\``) characters in regular expressions are interpreted
literally and do not escape anything or represent placeholders.
However, CMake language :ref:`Escape Sequences` such as ``\t``,
``\r``, ``\n``, and ``\\`` may be used to construct literal tabs,
carriage returns, newlines, and backslashes (respectively) to pass
in a regex. For example:
* The quoted argument ``"[ \t\r\n]"`` specifies a regex that matches
any single whitespace character.
* The quoted argument ``"[/\\]"`` specifies a regex that matches
a single forward slash ``/`` or backslash ``\``.
* The quoted argument ``"[A-Za-z0-9_]"`` specifies a regex that matches
any single "word" character in the C locale.
Manipulation Manipulation
^^^^^^^^^^^^ ^^^^^^^^^^^^