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";
}