Script to validate domains

Question

Objective is to read a list of domains from a file and perform lookup to confirm reachability and resolution from my end.

This is what I have written:

#!/usr/bin/python

import os
import socket

f = open('file1.lst', 'r')
s = f.readlines()

for i in s:
    print i
    socket.gethostbyname(i.strip())

f.close()

socket.gethostbyname() line throws an exception.

Answer 1

for i in s:
    print i
    try:
        socket.gethostbyname(i.strip())
    except socket.gaierror:
        print "unable to get address for", i

If an address could not be found, then gethostbyname will raise an exception (not throw). This is the way error handling is done in Python. If you know how to properly deal with the error, the you should catch it with an except clause.

Note that you will need some more code to also check for connectivity.

Answer 2

This is what I wrote to do the same thing. It may be of use to you:

import argparse
from socket import getaddrinfo

if __name__ == "__main__":
    parser = argparse.ArgumentParser(description='Check for validity of domains in list exported from exchange', version='%(prog)s 1.0')
    parser.add_argument('infile', nargs='+', type=str, help='list of input files')
    args = parser.parse_args()

    # Read domains from file
    domains = []
    for f in args.infile:
        with open(f, 'rt') as data:
            for line in data.readlines():
                split = line.replace('\x00',"").split(':')
                if split[0].strip() == 'Domain':
                    domains.append(split[1].strip())

    # Check each domain
    for domain in domains:
        try:
            getaddrinfo(domain, None)
        except Exception, e:
            print "Unable to resolve:", domain

Note that my input file has a slightly different format than yours, so you will need to adjust the input section.

Answer 3

You are passing the string 'i' to gethostbyname() rather than the variable i.

It should be socket.gethostbyname(i)

This question may be of use: Checking if a website is up via Python