How to get the IP address from /etc/hosts?

Question

I have the following line in my /etc/hosts file

54.230.202.149 gs2.ww.prod.dl.playstation.net

What I'm trying to do is, find the line gs2 in the /etc/hosts file and get the current IP address. This is what I have, but it doesn't find the DNS or return the IP address. It tells me that my current IP address is 'None'.

try:
     with open('/etc/hosts', 'r') as f:
         for line in f:
             host_ip = re.findall(r"\b(?:[0-9]{1,3}\.){3}[0-9]{1,3}\b.+(?=gs2)", line)
             if host_ip:
                 current_ip = host_ip[0].strip()
             else:
                 current_ip = 'None'
except:
    current_ip = 'Unknown'

c.execute('INTERT INTO status VALUES(?,?,?,?,?,?)',
           ('Current Configured IP', current_ip))

Not sure what the problem is. Any help would be appreciated.

Answer 1

Do this using .split(), which will split your line based on whitespace into separate indexed elements.

Also note that using this approach removes the need for host_ip[0].strip(), because all whitespace between IP address and hostname is removed during the split() operation. You can just use host_ip[0].

try:
     with open('/etc/hosts', 'r') as f:
         for line in f:
             host_ip = line.split()
             if host_ip and 'gs2' in host_ip[1][0:3]:
                 current_ip = host_ip[0]
             else:
                 current_ip = 'None'
except:
    current_ip = 'Unknown'

From https://docs.python.org/3/library/stdtypes.html#str.split:

(See URL for further discussion of split()).

str.split(sep=None, maxsplit=-1)

...

If sep is not specified or is None, a different splitting algorithm is applied: runs of consecutive whitespace are regarded as a single separator, and the result will contain no empty strings at the start or end if the string has leading or trailing whitespace. Consequently, splitting an empty string or a string consisting of just whitespace with a None separator returns [].

...

Answer 2

Your regex was working, I think the way the script was reading the lines was skewed a little bit as when I tested it didn't read my lines after a blank space. I ended up adding the lines variable. I am sure there is a more pythonic way to achieve this but it works.

import re

try:
    with open(r'/etc/hosts') as f:
        lines = [line for line in f.read().splitlines() if line]
        for line in lines:
            host_ip = re.findall(r"\b(?:[0-9]{1,3}\.){3}[0-9]{1,3}\b.+(?=gs2)", line)
            print(host_ip)
            if host_ip:
                current_ip = host_ip[0].strip()
                print(current_ip)
except:
    current_ip = 'Unknown'