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Regular Expression Flavor Comparison – Detailed comparison of the most popular regular expression flavors; Regexp Syntax Summary; Online Regular Expression Testing – with support for Java, JavaScript, .Net, PHP, Python and Ruby; Implementing Regular Expressions – series of articles by Russ Cox, author of RE2; Regular Expression Engines
A regular expression (shortened as regex or regexp), [1] sometimes referred to as rational expression, [2] [3] is a sequence of characters that specifies a match pattern in text. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings , or for input validation .
Unlike keyword searching, regex searching is by default case-sensitive, does not ignore punctuation, and operates directly on the page source (MediaWiki markup) rather than on the rendered contents of the page. To perform a regex search, use the ordinary search box with the syntax insource:/regex/ or intitle:/regex/. The expression regex ...
Search for an exact string using a simple regexp; pretest a small search domain. Hack out a highly refined set of page characteristics with concern only for an exact count of pages; refine in a sandbox and on the search results page. The concept of a search domain plays an important part in all this. By default it is just article space, but in ...
Rather than use the search box, where entering an equals sign and a pipe character, and "quotes around phrases" is a straightforward matter, it is still easiest to use a regex-based search-link template — {{}} or {{}} — on the page with sample data, because then you can focus on the target data there and on writing the regexp pattern.
Regex searches are likely to time out unless you further limit the search in some way, such as by including another parameter or a search term outside of the insource component of the search string. (For example, X* intitle:/X/ to restrict the search to initial position.) For more details, see mw:Help:CirrusSearch#Regular expression searches.
grep is a command-line utility for searching plaintext datasets for lines that match a regular expression.Its name comes from the ed command g/re/p (global regular expression search and print), which has the same effect.
Regular languages are a category of languages (sometimes termed Chomsky Type 3) which can be matched by a state machine (more specifically, by a deterministic finite automaton or a nondeterministic finite automaton) constructed from a regular expression. In particular, a regular language can match constructs like "A follows B", "Either A or B ...