Programming Forums - domain existence

Programming Forums (http://www.programmingforums.org/forumindex.php)

- Bash / Shell Scripting (http://www.programmingforums.org/forum26.html)

- - domain existence (http://www.programmingforums.org/showthread.php?t=11417)

domain existence

How could I check if a DNS domain exists? dig doesn't work because my DNS servers (OpenDNS) return the IP of their search server.

Do you want to check the existence of any domain - nslookup?
Options let you specify a domain to limit the search. You can also specify the
DNS box.

I'm not sure what you meant by a DNS domain in this context....

nslookup isn't what I want, but its man page pointed me to host, which is exactly what I wanted.

:/ host doesn't handle LAN IPs or aliases in /etc/hosts.

Check out 'man gethostbyname'. I believe that this library uses the standard DNS lookup stack in *nix (typically in /etc/host.conf).

Umm... this is the shell forum, not the C forum.

Quote:

Originally Posted by a thing (Post 115323)

Umm... this is the shell forum, not the C forum.

If the problem cannot be solved with existing shell tools, then you may need to write your own. ;)

If you just simply want to see if a domain name resolves, you can use something like:

ping $DOMAIN -c1 | grep ^PING | \

awk -F\  '{ gsub( /\(/,// , $3); gsub( /\)/,//,$3 ); print $3 }'

That returns the IP address of the domain. If the domain does not resolve, you get:

ping: unknown host googlaoeuaoee.com

If you do not care what the IP is, you can simply use ping:

#!/bin/bash



ping -c1 $1 >> /dev/null



if [ $? == 2 ]; then

    echo "$1 does not exist."

else

    echo "$1 exists."

fi

Hope this helps. :cool:

Quote:

Originally Posted by me

my DNS servers (OpenDNS) return the IP of their search server

notroot@arthur[0:~]$ ping -c1 asdr.ear.baawer

PING asdr.ear.baawer (208.67.219.40) 56(84) bytes of data.

64 bytes from ip-208-67-219-40.n.opendns.com (208.67.219.40): icmp_seq=1 ttl=50 time=14.1 ms



--- asdr.ear.baawer ping statistics ---

1 packets transmitted, 1 received, 0% packet loss, time 0ms

rtt min/avg/max/mdev = 14.197/14.197/14.197/0.000 ms

notroot@arthur[0:~]$ echo $?

0

notroot@arthur[0:~]$

Quote:

Originally Posted by a thing (Post 115720)

notroot@arthur[0:~]$ ping -c1 asdr.ear.baawer

PING asdr.ear.baawer (208.67.219.40) 56(84) bytes of data.

64 bytes from ip-208-67-219-40.n.opendns.com (208.67.219.40): icmp_seq=1 ttl=50 time=14.1 ms



--- asdr.ear.baawer ping statistics ---

1 packets transmitted, 1 received, 0% packet loss, time 0ms

rtt min/avg/max/mdev = 14.197/14.197/14.197/0.000 ms

notroot@arthur[0:~]$ echo $?

0

notroot@arthur[0:~]$

That clears things up a bit. Whether the domain exists or not has no bearing on OpenDNS's reply. That is quite crappy. Short of using your own DNS servers (or your ISP's), putting two and two together should work for you:

-'host' can resolve the IP of any FQDN given it
-'ping' can resolve the IP of any local DN (that you may specify in /etc/hosts)

host + ping + glue = solution ;)

Edit:

Playing around a bit more with OpenDNS as my nameserver, it appears to only return its search server IPs when the domain is not found. This being the case, you can still solve this with one tool (ping) and some parsing of the results (if $IP is in $IPS_OWNED_BY_OPENDNS....). :cool:

Your proposed solution has given me a better idea. Ping gives the packet loss percent. All I need to do is check if that's like <=15.

Damn I should learn awk.