Regular Expression Go to the previous , next section.
Patterns are described by regular expressions written using the same notation that the GNU Emacs text editor uses. This is handy, because you can try out a regular expression in the Emacs editor before coding it in your program. Regular expressions have a syntax in which a few characters are special constructs and the rest are ordinary . An ordinary character is a simple regular expression which matches that character and nothing else. Any two regular expressions a and b can be concatenated.