How to generate random strings that match a given regexp?

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Published on 2009-04-14T15:57:23Z Indexed on 2010/06/11 19:23 UTC
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Random string that matches a regexp

No, it isn't. I'm looking for an easy and universal method, one that I could actually implement. That's far more difficult than randomly generating passwords.

I want to create an application that takes a regular expression, and shows 10 randomly generated strings that match that expression. It's supposed to help people better understand their regexps, and to decide i.e. if they're secure enough for validation purposes. Does anyone know of an easy way to do that?

One obvious solution would be to write (or steal) a regexp parser, but that seems really over my head.

I repeat, I'm looking for an easy and universal way to do that.

Edit: Brute force approach is out of the question. Assuming the random strings would just be [a-z0-9]{10} and 1 million iterations per second, it would take 65 years to iterate trough the space of all 10-char strings.

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