In computing, a regular expression is a specific pattern that provides concise and flexible means to "match" (specify and recognize) strings of text, such as particular characters, words, or patterns of characters. Common abbreviations for "regular expression" include regex and regexp.
The concept of regular expressions was first popularized by utilities provided with Unix distributions, in particular the editor ed and the filter grep. A regular expression provides a grammar for a formal language; this specification can be interpreted by a regular expression processor, which is a program t...