dig google.com dig google.com +short
Can also do reverse DNS with dig
dig -x 1.2.3.4 dig -x 1.2.3.4 +short
host is another similar program
host google.com
You can do reverse DNS with host by just using the IP.
host 1.2.3.4
nslookup is like host and dig, but interactive.
nslookup
You can do the following anyway
nslookup google.com
nslookup 1.2.3.4