There are different versions of host so that might be the explanation. The idea is workable, though; get the verbose (debugging) output and parse out the fields you want. But in any case, to get the name and IP address of the name servers, you will need multiple queries -- one to get the names of the name servers, and another to look up their IP addresses. (Some sites put raw IP addresses in the NS records but this is strongly discouraged.)
I think Ikon misunderstood your question, perhaps because the output format you are suggesting is somewhat misleading (perhaps it should mention that these are the IP addresses of the name servers). The pipeline could be simplified a bit but the request of A records instead of NS records is wrong anyway.
I think you're getting the wrong result somehow; at least for me, b.iana-servers.net is 193.0.0.236 -- you're querying for $dom which is wrong, you should be querying for $server, but there can be other complications, too.
dig and host are not part of coreutils; on Ubuntu, at least, they're in the dnsutils and host packages, respectively, and there's also a separate bind9-host package which I believe contains a different version of host (hence, different output formats; originally host was also part of the dnsutils package, but many people wanted the Bind version, so they split it out).
Last edited by era; 08-23-2008 at 02:11 PM..
Reason: Observe that $dom should be $server