As regular expressions grow in complexity, regex generators can make the job easier by computing the patterns for you.
A regular expression (regex)  is a sequence of characters that describes a search pattern. You can use a regex to save time searching and replacing in texts, such as strings in programming languages, database query results, or normal documents. Regexes also can help you effectively use utilities, such as
xmlgrep , and
Ultimately, a regex’s usefulness depends on the pattern you select. Formulating a regex that delivers precise results is no easy task (see the “DIY Regular Expressions” box). To save time, a regex generator can automate this step for you by taking a text/character string and deriving a suitable regular expression.
Regex generators work with varying degrees of precision. Some regex generators offer maximum precision, where the regular expression finds exactly one pattern. Others offer minimum precision, where the regex finds a set of patterns with a similar structure. In this article, I test several regex generators to determine how well they work (see also the “Nonfunctional” box).
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