Appendix: Regular Expressions

A regular expression (abbreviated as regexp or regex) is a string that describes a whole set of strings, according to certain syntax rules. These expressions are used by many text editors and utilities (especially in the Unix operating system) to search bodies of text for certain patterns and, for example, replace the found strings with a certain other string.

• • Brief History
  • Regular Expressions in Formal Language Theory
  • POSIX Regular Expression Syntax