A P P E N D I X
This appendix introduces regular expressions in a quick and practical manner. This introduction is only the beginning, however, as the subject is so extensive that entire books have been written on it. A good example is Regular Expression Recipes by Nathan A. Good (Apress, 2004). Regular expressions (regexes) are a method for precisely matching strings that fit certain selection criteria. They are an old concept from theoretical computer science and are based on finite state machines.
There are many varieties of regular expressions, and they are different in many respects. The two most frequently encountered regular expression engines are Posix regular expressions and Perl compatible regular expressions (PCRE). ...