Python - store output of subprocess() call in a string

Question

Hey all, I'm trying to make a system call in Python and store the output to a string that I can manipulate in the Python program.

#!/usr/bin/python

import subprocess

p2 = subprocess.Popen("ntpq -p")

I've tried a few things including some of the suggestions here:

http://stackoverflow.com/questions/1996518/retrieving-the-output-of-subprocess-call

but without any luck.

Many thanks!

Answer 1

The os.cwd() function does what you are trying to accomplish with this call, and in a more portable manner to boot.

Anyway, like the answer you linked to suggests, pass the PIPE argument to the Popen constructor. Then you can read from p.stdout as from any other file-like object. Something like this (untested):

p2 = subprocess.Popen("ntpq -p", stdout = subprocess.PIPE)
output = p2.stdout.read()

Answer 2

This worked for me for redirecting stdout (stderr can be handled similarly):

from subprocess import Popen, PIPE
pipe = Popen(path, stdout=PIPE)
text = pipe.communicate()[0]

If it doesn't work for you, please specify exactly the problem you're having.

Answer 3

Assuming that pwd is just an example, this is how you can do it:

import subprocess

p = subprocess.Popen("pwd", stdout=subprocess.PIPE)
result = p.communicate()[0]
print result

See the subprocess documentation for another example and more information.

Answer 4

Use the communicate method.

import subprocess
p = subprocess.Popen(["ntpq", "-p"], stdout=subprocess.PIPE)
out, err = p.communicate()

out is what you want.

Note how I passed in the command. The "ntpq -p" example brings up another matter. Since Popen does not involke the shell, you would use a list of the command and options—["ntpq", "-p"].

Answer 5

 import os   
 list = os.popen('pwd').read()

In this case you will only have one element in the list.