Dig

dig (domain information groper) is a network administration command-line tool for querying Domain Name System (DNS) name servers.

Example usage
In this example, dig is used to query for any type of record information in the domain example.com:

Command line: dig example.com any Output:
 * <<>> DiG 9.6.1 <<>> example.com any
 * global options: +cmd
 * Got answer:
 * ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4016
 * flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0


 * QUESTION SECTION:
 * example.com.                  IN      ANY

example.com. 172719 IN      NS      a.iana-servers.net. example.com. 172719 IN      NS      b.iana-servers.net. example.com. 172719 IN      A       208.77.188.166 example.com. 172719 IN      SOA     dns1.icann.org. hostmaster.icann.org. 2007051703 7200 3600 1209600 86400
 * ANSWER SECTION:


 * Query time: 1 msec
 * SERVER: ::1#53(::1)
 * WHEN: Wed Aug 12 11:40:43 2009
 * MSG SIZE rcvd: 154

Queries may be directed to designated DNS servers for specific records; in this example, MX records:

Command: dig wikimedia.org MX @ns0.wikimedia.org Output:
 * <<>> DiG 9.6.1 <<>> wikimedia.org MX @ns0.wikimedia.org
 * global options: +cmd
 * Got answer:
 * ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 61144
 * flags: qr aa rd; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 2
 * WARNING: recursion requested but not available


 * QUESTION SECTION:
 * wikimedia.org.                IN      MX

wikimedia.org. 3600   IN      MX      10 mchenry.wikimedia.org. wikimedia.org. 3600   IN      MX      50 lists.wikimedia.org.
 * ANSWER SECTION:

mchenry.wikimedia.org. 3600   IN      A       208.80.152.186 lists.wikimedia.org. 3600   IN      A       91.198.174.5
 * ADDITIONAL SECTION:


 * Query time: 73 msec
 * SERVER: 208.80.152.130#53(208.80.152.130)
 * WHEN: Wed Aug 12 11:51:03 2009
 * MSG SIZE rcvd: 109