To lookup the IP number for a domain name, use dig (domain internet grapher).
For full DNS infromation for the site, use: dig DOMAIN Where DOMAIN is the domain you want to look up.
To return just the IP address, use: dig +short DOMAIN Example: dig +short ojb.nz, gives 121.99.240.66
Alternatively, use: dscacheutil -q host -a name DOMAIN Where DOMAIN is the domain you want to look up. Note: This might give a different result, depending on cacheing.