pass data among processes in python

Question

I'm trying to get familiar with subprocess.Popen mechanism.

In the bellow example, I try to run netstat then run grep on the output.

netstat = subprocess.Popen("netstat -nptl".split(), stdout = subprocess.PIPE)
grep = subprocess.Popen("grep 192.168.46.134".split(), stdin = subprocess.PIPE)

However this does not result in a desired output.

Answer 1

You need to reference the first process' stdout as the stdin for the second process:

import subprocess

netstat = subprocess.Popen("netstat -nptl".split(), stdout=subprocess.PIPE)
grep = subprocess.Popen("grep 192.168.46.134".split(), stdin=netstat.stdout, stdout=subprocess.PIPE)

stdout, stderr = grep.communicate()
print stdout # this is a string containing the output