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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 .
A regex search scans the text of each page on Wikipedia in real time, character by character, to find pages that match a specific sequence or pattern of characters. 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 ...
Advanced when All (namespaces) is checked is equivalent to Everything. Multimedia searches the File and Media namespaces on the local wiki plus Commons. These differ from namespace "all" by matching your search terms inside a pdf on a help:file page, that item on the search results page says "(matches file content)".
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. It is ...
Patterns in PCRE2 can match these properties: e.g. \ p {Ps}.*? \ p {Pe} would match a string beginning with any "opening punctuation" and ending with any "close punctuation" such as [abc]. Matching of certain "normal" metacharacters can be driven by Unicode properties when the compile option PCRE2_UCP is set.
Standard library includes PCRE-based Regex module. The matching algorithms of the library are based on the PCRE library, but not all of the PCRE library is interfaced and some parts of the library go beyond what PCRE offers. Currently PCRE version 8.40 (release date 2017-01-11) is used. Erlang: erlang.org: Apache 2.0
As an ad hoc sandbox, you can show the wikitext of a section like this, (already saved in the database), modify some of the patterns in the regex-search-link template calls on this page, do a Show Preview, and see what matches when you click on the newly formed regex search-link, all quite safely, and without changing a thing in the database.
Copy the list of results and put it into a separate one-column table as described in the previous section. Then copy that column and use it to replace the code column as described here: §§ Help:Tables and Copy column from one table to another. The table will need to be alphabetized again since the codes alphabetize differently versus the full ...