Using the dig command in python

Question

Just a forewarning, my python skills are almost nonexistent, but I’m trying to learn as I go.

I'm doing a few changes via our DNS control panel over the weekend to about 58 CNAMES (just changing the destination)

And rather than checking the changes have gone live for each individual record I was wondering if there was a way to script a list of digs for each CNAME in python?

The dig command I use would be something like this

dig @ns1.netnames.net www.rac.co.uk CNAME

and I would expect to see rac-secure.gslb2.rac.co.uk returned.

I tried something like:

import os
os.system( 'dig<exampledomain.com>'CNAME )

But that didn't appear to work (as I mentioned my python skills are lacking), am I on the right path, or should I be using something like dnspython? I have used the dnspython module before with (a lot) of help from the stack overflow community but I find the documentation really confusing.

Any pointers in the right direction would be greatly appreciated.

Regards

Chris.

koblas · Accepted Answer · 2013-06-04T16:29:02.320

56

It's quite possible to invoke dig from python, it would probably save you work to just use a python library. Take a look at dnspython which will probably do everything easier - plus you don't have to parse the output format.

import socket
import dns.resolver

# Basic query
for rdata in dns.resolver.query('www.yahoo.com', 'CNAME') :
    print rdata.target

# Set the DNS Server
resolver = dns.resolver.Resolver()
resolver.nameservers=[socket.gethostbyname('ns1.cisco.com')]
for rdata in resolver.query('www.yahoo.com', 'CNAME') :
    print rdata.target

edited Jun 04 '13 at 16:29

answered Mar 08 '11 at 19:07

koblas

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Just to clarify, does the #basic query just check what your isp reports and the #set dns server check what the name server is reporting? – Christopher Long Mar 09 '11 at 11:28
The basic query uses your default /etc/resolv.conf name servers, while the Set version allows you to specify which nameserver to call. – koblas Mar 09 '11 at 13:16
1

It should be dnspython instead of dynpython. but the 6 char limits in SO stops me from editing the answer above. – Yudong Li Jun 04 '13 at 05:00
You need to install https://pypi.org/project/dnspython3/ to be working with python 3 – Elmux Jan 08 '19 at 20:45

unutbu · Answer 2 · 2011-03-08T17:08:19.897

8

os.system is deprecated. Use subprocess.Popen:

import subprocess
import shlex

cmd='dig @ns1.netnames.net www.rac.co.uk +short'
# cmd='dig @ns1.netnames.net www.rac.co.uk CNAME'
proc=subprocess.Popen(shlex.split(cmd),stdout=subprocess.PIPE)
out,err=proc.communicate()
print(out)
# rac-secure.gslb.norwichunion.com.

edited Mar 08 '11 at 17:08

answered Mar 08 '11 at 16:59

unutbu

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I get a fairly large error when trying to run that: **Traceback (most recent call last): File "C:/Users/Chris/Documents/work/python/cname.py", line 5, in proc=subprocess.Popen(shlex.split(cmd),stdout=subprocess.PIPE) File "C:\Python26\lib\subprocess.py", line 623, in __init__ errread, errwrite) File "C:\Python26\lib\subprocess.py", line 833, in _execute_child startupinfo) WindowsError: [Error 2] The system cannot find the file specified** – Christopher Long Mar 08 '11 at 17:33
1

The error: `[Error 2] The system cannot find the file specified` implies (or at leasts suggests) that you don't have an executable named `dig`. – unutbu Mar 08 '11 at 19:12
Ah, I just tried this at work and it works perfectly, must be something to do with my home desktop. Thank you. – Christopher Long Mar 09 '11 at 11:30

score 1 · Answer 3 · answered Oct 20 '21 at 18:19

Found 2 additional Python libraries for dig-like commands.
Both of them are called pydig.

1 ) leonsmith/pydig

Installation:
pip install pydig

Usage:

>>> import pydig
>>> pydig.query('example.com', 'A')
['93.184.216.34']
>>> pydig.query('www.github.com', 'CNAME')
['github.com.']
>>> pydig.query('example.com', 'NS')
['a.iana-servers.net.', 'b.iana-servers.net.']

2 ) shuque/pydig.

Installation:
(as root) python3 setup.py install

Usage:

   pydig www.example.com
   pydig www.example.com A
   pydig www.example.com A IN
   pydig @10.0.1.2 example.com MX
   pydig @dns1.example.com _blah._tcp.foo.example.com SRV
   pydig @192.168.42.6 +dnssec +norecurse blah.example.com NAPTR
   pydig @dns2.example.com -6 +hex www.example.com
   pydig @192.168.72.3 +walk secure.example.com

Using the dig command in python

3 Answers3