Не понимаю в чем сложность...

[root@host test]# cat > hostnames
mail.ru
ya.ru
ru.ru
[root@host test]# cat hostnames |while read d; do nslookup $d; done
Server:         ns1.domain.ru
Address:        XXX.XX.X.X#53

Non-authoritative answer:
Name:   mail.ru
Address: 194.67.57.26

Server:         ns1.domain.ru
Address:        XXX.XX.X.X#53

Non-authoritative answer:
Name:   ya.ru
Address: 213.180.204.8

Server:         ns1.domain.ru
Address:        XXX.XX.X.X#53

Non-authoritative answer:
Name:   ru.ru
Address: 195.2.72.149

MyHomePage - http://surgutnet.ru