for IP in $(cat IP.text | sort | uniq); do if [ $(nslookup $IP | egrep "^Name:" | wc -l) -eq "1" ]; then DN=$(nslookup $IP | egrep "^Name:" | sed 's/.*\ //g'); else DN="NA"; fi; echo "${IP//[$'\t\r\n']} ${DN//[$'\t\r\n']}"; done 2>/dev/null