This recipe is about the dig command in Unix and some useful examples, which you can find interesting when scripting or when need to check your address from inside the machine that you are accessing by the private network.

dig is an acronym for Domain Information Groper and is a command-line utility that performs DNS lookup by querying name servers and displaying the result to you. It is part of the dnsutils package in Debian, make sure you have that installed.

The syntax is:

dig [@server] [-b address] [-c class] [-f filename] [-k filename] [-m] [-p port#] [-q name] [-t type] [-x addr] [-y [hmac:]name:key] [-4] [-6] [name] [type] [class] [queryopt...] 

Some examples:

To get you ip adress, using the server resolver1.opendns.com:

dig @resolver1.opendns.com ANY myip.opendns.com +short

Get the address for bigg.blog

dig bigg.blog A +noall +answer

Command to get a list of the mailservers for bigg.blog

dig bigg.blog MX +noall +answer

The following command is to get a list of authoritative DNS servers for bigg.blog

dig bigg.blog NS +noall +answer

To get a list of all the above (MX and NS) at once

dig bigg.blog ANY +noall +answer 

Trace the path taken to resolve the name

dig bigg.blog +trace

Reverse lookup

dig +answer -x 104.24.116.215

Query names from a file

dig -f domain_list.txt +short

To customise permanently the output, you need to create a file ~/.digrc like

echo "+noall +answer" > ~/.digrc

Now, when dig is executed it will show only answer section will output.

Hope it helps you
Have a great day

-G