subdomain.domain.tld regexp?

[John Bokma]

Is there a module that can split a given host in a subdomain, domain, tld
part?

e.g.

[url]www.google.com[/url] => www google com
[url]www.google.co.uk[/url] => www google.co uk
[url]www.google.nl[/url] => www google nl
[url]www.asus.com.tw[/url] => www asus.com tw

(yup, technically the com? is probably the domain, and www a sub-sub
domain)

--
John Small Perl scripts: [url]http://johnbokma.com/perl/[/url]
Perl programmer available: [url]http://castleamber.com/[/url]
Happy Customers: [url]http://castleamber.com/testimonials.html[/url]

[Brian McCauley]

John Bokma wrote:

> Is there a module that can split a given host in a subdomain, domain, tld
> part?
>
> e.g.
>
> [url]www.google.com[/url] => www google com
> [url]www.google.co.uk[/url] => www google.co uk
> [url]www.google.nl[/url] => www google nl
> [url]www.asus.com.tw[/url] => www asus.com tw
>
> (yup, technically the com? is probably the domain, and www a sub-sub
> domain)

DNS is strictly hierachical. As far as DNS is concerned 'uk', 'co.uk',
'google.co.uk' and 'www.google.co.uk' are all just domains.

You need to take a step back and consider what you really want to do. I
suspect you have no idea.

To split a dot-delimited string into a list of components:

my @components = split /\./, $domain_name;

Do you perhaps want to find the DNS zone boundries? If so why do you
think this would be helpful?

[John Bokma]

Brian McCauley wrote:

> John Bokma wrote:
>

>> Is there a module that can split a given host in a subdomain, domain,
>> tld part?
>>
>> e.g.
>>
>> [url]www.google.com[/url] => www google com
>> [url]www.google.co.uk[/url] => www google.co uk
>> [url]www.google.nl[/url] => www google nl
>> [url]www.asus.com.tw[/url] => www asus.com tw
>>
>> (yup, technically the com? is probably the domain, and www a sub-sub
>> domain)

>
> DNS is strictly hierachical. As far as DNS is concerned 'uk',
> 'co.uk', 'google.co.uk' and 'www.google.co.uk' are all just domains.

Yeah I know.

> You need to take a step back and consider what you really want to do.
> I suspect you have no idea.

Because you don't have an idea doesn't mean I haven't one.

I want to get the part one can register as, say, a company.

in the uk I can't register

somename.uk

but I can register:

somename.co.uk

In nl however, I can register:

somename.nl

--
John Small Perl scripts: [url]http://johnbokma.com/perl/[/url]
Perl programmer available: [url]http://castleamber.com/[/url]
Happy Customers: [url]http://castleamber.com/testimonials.html[/url]

[Brian McCauley]

John Bokma wrote:

> Brian McCauley wrote:
>
>

>>John Bokma wrote:
>>
>>

>>>Is there a module that can split a given host in a subdomain, domain,
>>>tld part?
>>>
>>>e.g.
>>>
>>>[url]www.google.com[/url] => www google com
>>>[url]www.google.co.uk[/url] => www google.co uk
>>>[url]www.google.nl[/url] => www google nl
>>>[url]www.asus.com.tw[/url] => www asus.com tw
>>>
>>>(yup, technically the com? is probably the domain, and www a sub-sub
>>>domain)

>>
>>DNS is strictly hierachical. As far as DNS is concerned 'uk',
>>'co.uk', 'google.co.uk' and 'www.google.co.uk' are all just domains.

>
>
> Yeah I know.
>
>

>>You need to take a step back and consider what you really want to do.
>>I suspect you have no idea.

>
> Because you don't have an idea doesn't mean I haven't one.

No, but the fact that your OP does not convey your idea is often a good
sign that you haven't actually crystalised your idea.

> I want to get the part one can register as, say, a company.

This is a question about the policy of issuing subdomains under a
domain. There may or may not be a standard way for a domain to publish
its subdomain policy. There certainly is no widely used standard.
If there were a widely used standard then there could be a Perl module
to interface to it.

> in the uk I can't register
>
> somename.uk

You can't, but some entities can. Sufficiently few uk 2nd-LDs are
issued I suspect each application is considered on it's merits rather
than there being a simple algotithm.

There are also domains like ac.uk which accept registrations from a
restricted class of entities.

Someone could compose a list of domains that accept subdomain
registration from the general populace but this could simply be a plain
text file rather than a Perl module.

Note: there are situations like uk.com where both uk.com and com accept
registrations.

[Carl Corliss]

@Brian McCauley: How about reading between the lines a little and providing a /helpful/ answer instead of rhetoric. It's not that hard to see that what he wants is just the domain part of a domain name and not the host part.

@John Bokma: While there is no perl module that I am aware of that will give you what you seek, you can certainly get most of the way there with regular expressions:

foreach (qw(a.b.co.uk a.b.uk.com a.b.com b.co.uk b.uk.com b.com z.y.x.a.b.c.co.uk z.y.x.a.b.c.uk.com) ) {
  printf("%-19s: %s\n", $_, ($_ =~ m/
    (?|                                              # branch reset (perl 5.10+ specific), also doesn't count as a capture group
      (?=^[a-z][a-z0-9-]*\.[a-z]{2,3}$)(.*)          # check for domain.tld or domain.tl and capture it (as $1)
      |                                              
      (?:^[a-z][a-z0-9-]*\.)*?                       # skip past subdomain parts (with a non capturing group)
      (?|                                            # branch reset (perl 5.10+ specific), also doesn't count as a capture group 
       (?=[a-z][a-z0-9-]*\.[a-z]{2}\.[a-z]{2,3})(.*) # look ahead for host.uk.com or host.co.uk and capture it
       |                                             
       (?=[a-z][a-z0-9-]*\.[a-z]{3})(.*)             # look ahead for host.com and capture it
      )
    )$
  /x ? $1 : "no match")); 
}

Cheers!,

--
Carl