5.34 How do I use regexps (regular expressions) in Emacs?
See Regexp Backslash in The GNU Emacs Manual.
or operator is ‘\|’, not ‘|’, and the grouping operators
are ‘\(’ and ‘\)’. Also, the string syntax for a backslash is
‘\\’. To specify a regular expression like ‘xxx\(foo\|bar\)’
in a Lisp string, use ‘xxx\\(foo\\|bar\\)’.
Note the doubled backslashes!
- Unlike in Unix grep, sed, etc., a complement character set
(‘[^...]’) can match a newline character (LFD a.k.a.
C-j a.k.a. ‘\n’), unless newline is mentioned as one of the
characters not to match.
- The character syntax regexps (e.g., ‘\sw’) are not
meaningful inside character set regexps (e.g., ‘[aeiou]’). (This
is actually typical for regexp syntax.)