How to determine if two host names are in the same domain

How to write code to decide if two host name in same domain ?

like :

www.example.com an开发者_如何学Cd login.eample.com in same domain

www.example.com.us and login.exmaple.com.us in same domain

x105.www.example.com and login.example.com in same domin

and even www.example.com and login.example.com.us in same domain if possible

---

Using perl since no language was mentioned, pardon any rust...

([^.]+\.[^.]+$)

that regex would give you the domain of the first instance as a captured string ($1). You could use that captured string, if this was say perl, like this to see if they match.

$firstHostName =~ /([^.]+\.[^.]+$)/;
if ($secondHostName =~ /$1$/) {
    print "same domain";
}