Lookup hostname from IP address

Geneset · 08-25-2008, 02:03 PM

Hi guys
I'm writing a script to parse the ip table from my router but I'm up against a brick wall of how to easily convert from an ip address to a hostname.

whois creates alot of output and is not standardised really, I'm just simply looking to get from xxx.xx.xx.xx to computer.domain.tld

any ideas?

Cheers

CRC123 · 08-25-2008, 02:07 PM

Try the 'nslookup' command. It should give you the human readable hostname as part of its output as long as your nameserver is setup correctly.

rocket357 · 08-25-2008, 02:07 PM

Quote:

Originally Posted by Geneset

Hi guys
I'm writing a script to parse the ip table from my router but I'm up against a brick wall of how to easily convert from an ip address to a hostname.

whois creates alot of output and is not standardised really, I'm just simply looking to get from xxx.xx.xx.xx to computer.domain.tld

any ideas?

Cheers

host xxx.xxx.xxx.xxx | cut -d' ' -f5

Geneset · 08-25-2008, 02:34 PM

Thanks rocket thats a charmer.

Had just found rhost in the jdresolve package but its far too slow.
thats perfect.
Much appreciated, but can you guys cast ur mind to this also?

chort · 08-25-2008, 03:01 PM

Code:

$ dig +short -x <ip address>

works too. Don't use nslookup for anything, it's deprecated and due to be replaced. Learn to use dig instead.

PS Be aware that you'll get an empty string if there is no PTR record for the IP address, so you script has to know that an empty response from dig means that there's no PTR for the IP.

Geneset · 08-26-2008, 05:03 AM

Cheers, using dig, works great. Wish more people had stuff like this documented online, i spent about 30 minutes googling "lookup hostname from ip unix" "reverse dns unix ip hostname".... and so the list of polymorphic combinations went on....

ALWAYS DEAL WITH A PERSON, lol <SOLVED>