Macintosh Terminal Pocket Guide

Name

host — stdin  stdout  - file  -- opt  --help  --version

Synopsis

host [options] name [server]

The host command looks up the hostname or IP address of a remote machine by querying DNS:

➜ host apple.com
apple.com has address 17.172.224.47
apple.com has address 17.149.160.49
➜ host 17.172.224.47
47.224.172.17.in-addr.arpa domain name pointer apple.com.

It can also find out much more:

➜ host -a apple.com
Trying "apple.com"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2915
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, ...

;; QUESTION SECTION:
;apple.com.                     IN      ANY

;; ANSWER SECTION:
apple.com.      2003    IN      A       17.172.224.47
apple.com.      2003    IN      A       17.149.160.49

Received 59 bytes from 192.168.1.1#53 in 20 ms

though a full discussion of this output is beyond the scope of this book. The final, optional “server” parameter specifies a particular nameserver for the query:

➜ host apple.com nserver.apple.com
Using domain server:
Name: nserver.apple.com
Address: 17.254.0.50#53
apple.com has address 17.149.160.49
...

To see all options, type host by itself.

Useful options

-a	Display all available information.
-t	Choose the type of nameserver query: A, AXFR, CNAME, HINFO, KEY, MX, NS, PTR, SIG, SOA, and so on.

Here’s an example of the -t option to locate MX records:

➜ host -t MX apple.com
apple.com mail is handled by 10 mail-in11.apple.com.

If the host command doesn’t do what you want, try dig, another powerful DNS lookup utility. There’s also the nslookup command, mostly obsolete but still available in OS X.