Is there a public domain version of regex(3) ?

[Guido van Rossum]

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I am writing an editor which, for compatibility's sake, must include a
regular expression matching function exactly as that in ed(1) (with which
our secretaries grew up -- not the most progressive force in the world. :-)

BSD unix systems document this as regex(3), but I don't want to make
my code dependent on BSD, or even unix, for that matter.
I can't just put a copy of BSD's regex.c in my distribution, because
this would violate all sorts of copyright restrictions (I suppose).

So...

Does anyone know of a public domain program which does the same?
(If not, I guess I'll write it myself, but it's not my idea of fun.)

--
	Guido van Rossum, CWI, Amsterdam
	guido at mcvax.UUCP

"You're right.  But you're boring."