Re: Random passwords and E-mail regex

["Dana M. Diederich" <dana@realms.org>]

> Regular expression for E-mail address checking - here's what I came up
> with.  I have not tested it yet, and am not extremely familiar with
> regexes.  Anyone want to take a look and see if it can be improved upon?
> 
> if (!ereg("^\w+@\w+\.\w+$", $email))
> 
> (this is PHP remember, not Perl.  Hopefully the regex syntax is the
> same)
> 
The way to do this is to just use the perl module Net::DNS to do an MX lookup
on the stuff right of the @ sign.  If that works, the right part is verified.
The stuff on the left is a lot more free form.  You have to allow just about
anything printable, because of all of the non RFC compliant mailers out there.

The perl regular expression implemention is a huge superset of the most 
commonly used library from Henry Spencer, 'Version 8 Regular Expressions.'
I don't think any language even comes close.

As far as how to use a perl module from PHP, I suspect there are a few options.
Worst case is writing a separate perl script which your PHP script calls as
a shell.  Or maybe there's a PHP DNS module.

If you still want to do some very loose validation without doing a MX lookup,
I'd suggest looking at the DNS RFC.  I don't know the number off hand, but
I could find out.  

Cheers.
-Dana
-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,
Dana M. Diederich        Phone: 1.501.855.7175
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`Berkeley invented LSD and Unix, and I don't think that's a coincidence.'