os.popen subprocess conversion

Question

Hi Pythoners.

This snippet gets me the dotted quad of my BSD network interface. I would like to figure out how to use the subprocess module instead.

ifcfg_lines = os.popen("/sbin/ifconfig fxp0").readlines()
x = string.split(ifcfg_lines[3])[1]

Seems as if I can't use subprocess in exactly the same way. I don't think I want shell=True or PIPE. What should I do to make the output indexable?

Thanks.

Answer 1

Why not use something like:

import socket
ipadr = socket.gethostbyname(socket.gethostname())

as in Finding Local IP Addresses in Python and remove the subprocess dependency? There are also some other suggestions in that question.

I also found a post on the netifaces package that does aims to do this with better cross-platform support.

Answer 2

from subprocess import Popen, PIPE

ifcfg_lines = Popen("/sbin/ifconfig fxp0",shell=True,stdout=PIPE).stdout.readlines()
x = string.split(ifcfg_lines[3])[1]

For a little more elegance, hide the details:

def getBSDIP():
   from subprocess import Popen, PIPE
   import string

   CURRENT = Popen("/sbin/ifconfig fxp0", shell=True,stdout=PIPE).stdout.readlines()
   return(string.split(CURRENT[3])[1])

If you are going to use subprocess to do this then elegance is a bit limited because you are essentially doing something like screenscraping, except here you are scriptscraping. If you want a truly general solution, use the socket library, i.e. let Python handle the portability.

Often, when you look at a bit of code and you wish that there was a better cleaner way to do it, this means that you need to question your assumptions, and change the algorithm or architecture of the solution.