parsing a dns configuration file with python

Question

Not sure this question has it's place, but i'll give it a shot anyway. Basically what I need is to parse a conf file.

It would look like this :

 1. #local-data: "some.dns.url IN MX 192.168.80.45"
 2. local-data: "some.other.dns.url IN A 192.168.60.1"
 3. local-data: "router.home.somewhere IN A 192.168.20.1"
 4. *a linebreak*
 5. local-data-ptr: "192.168.80.45 some.dns.url"
 6. local-data-ptr: "192.168.60.1 some.other.dns.url"
 7. # some other random comment
 8. local-data-ptr: "192.168.20.1 router.home.somewhere"

What i'd need to get off of it is : The address : "some.other.dns.url" on the 2nd line what is after the "IN" : that can be MX, A, some others. The IP : in that case 192.168.60.1, but that could be anything else.

I don't necessarily need the complete script. Hell I don't even really need one, that's not my goal posting here. I would like to know the best approach for such a case. Most of the time I tend to get out of situations like that, but this time this seems a bit tricky as :

I can't base myself on the size of the line.
I can't base myself on "dots" (.) for the address, as one could have 2 dots, and another one have 3.
I have part of the line ("IN") that is just disturbing and not of some use.

What i've done so far :

dnsconf = open('theconffile.conf', 'r')
dnsconf = dnsconf.readlines()
x = []
    for line in dnsconf:
        cont = re.findall('\"(.+?)\"', line)
        if len(line) > 1 and line[:1] is not '#':
           x.append(cont)
           print cont

cont basically contains what is inside the double quotes. "some.dns.url IN MX 192.168.80.45" for exemple.

I feel like this is a good start but I fail to see how to continue from there. I am not good with regexes and I feel like what I need are actually regexes...so i'm a little bit stuck here.

Can anyone put me on the right track for this problem?

Why not just .*\s+IN\s+(?:A|MX|...)\s+(.*?)"\s*$?

Kevin
– Kevin

2015-08-17 13:44:51 +00:00
Commented Aug 17, 2015 at 13:44 — Kevin
– Kevin, Commented Aug 17, 2015 at 13:44
Checked out pypi.python.org/pypi/iscpy?

wenzul
– wenzul

2015-08-17 13:47:18 +00:00
Commented Aug 17, 2015 at 13:47 — wenzul
– wenzul, Commented Aug 17, 2015 at 13:47

DisappointedByUnaccountableMod · Accepted Answer · 2015-08-17 14:29:03Z

1

This ignores the lines beginning with #, decode lines beginning 'local-data:', and parses out the hostname, DNS type and IP address to a list:

import re

dnsconf = open('dns.txt', 'rt')

x = []
for line in dnsconf:
    cont = re.findall('^local-data:\s+\"(\S+)\s+IN\s+(\S+)\s+(\S+)\"', line)
    if cont:
        x.append(cont)
        print cont

This allows spaces to be repeated within the strings by using \s+.

Output for your data is:

[('some.other.dns.url', 'A', '192.168.60.1')]
[('router.home.somewhere', 'A', '192.168.20.1')]

Note unless you have a reason to need all the text in memory there is no need to use readlines(). Also for Windows-robustness, using file open mode "rt" doesn't do any harm on unixy systems.

answered Aug 17, 2015 at 14:29

DisappointedByUnaccountableMod

6,8444 gold badges21 silver badges23 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Enjoyted Over a year ago

After plenty of tests, this seems to be what I was looking for. I just added '[#]?' at the beginning to catch comments that are correct lines too. Thank you !

DisappointedByUnaccountableMod Over a year ago

:-) I don't think you need the [ ] around # - just #? should work.

Collectives™ on Stack Overflow

parsing a dns configuration file with python

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related