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# Regular Expression

A regular expression is a text string that specifies a pattern of characters. This facility allows you to write J programs using regular expressions to search arbitrary text. You can perform a search for a single or multiple matches, or extract the matched text from the string. You can also merge new text in to replace the matches, or apply a verb to the matched text in a string.

Utility verbs are included to assist in building regular expression patterns, as is a utility to search J scripts and other text files for patterns.

The primary definitions are in `system\main\regex.ijs` ; utility verbs to build patterns are in `system\packages\regex\regbuild.ijs` .

The Find in Files utility, available from the Edit menu or by pressing Ctrl+Shift+F, can search for simple text, regular expression, or special patterns such as the assignment of a name.

Labs and a demo on regular expressions are available from the Studio menu.

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