Regular Expression for IPv6 addresses

Sat Feb 6 22:16:54 UTC 2010

Folks,

Thanks for all the comments on the IPv6 regex...

-----
>  Jeroen Massar <jeroen at unfix.org> wrote:
>
>  The only proper way of "testing" if an address is a valid IPv6 address
>  is to feed it to getaddrinfo() and then use it through that API.

Good point. One of the reasons to do this was for environments where getaddrinfo()  
might not be availble. (For example, in a Javascript - see the page on the InterMapper  
site: http://intermapper.com/ipv6validator )

>  Of course, there should be only limited places where a user can enter or
>  see IP addresses in the first place. There is this great thing called
>  DNS which is what most people should be using.

Another good point. But look at Seiichi's note (below)...

-----
>  Seiichi Kawamura <kawamucho at mesh.ad.jp> also> wrote:

>  This might be of some interest to you.
>
>  http://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-04

We believe this correctly recognizes all the cases specified by RFC4291. But it's  
a great idea to update the Javascript page above to reformat to this recommendation.

-----
>  Carsten Bormann <cabo at tzi.org>
>
>  I was looking at this regexp for my Ruby course as a great example of "how not
>  to use Regexps".
>
>  But thank you for this textbook example!
>  And, of course, an error did creep in.

You're quite welcome! :-)

But seriously... Do you have an example of an address that causes the RE to fail?

>  If you really need an RE, the right approach here is to write a small program  
>to
>  generate the RE.

Absolutely. The Perl program cited includes code much like your example.

Rich Brown                    richard.e.brown at dartware.com
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