Store output of subprocess.Popen call in a string

Question

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:

Retrieving the output of subprocess.call()

but without any luck.

Answer 1

I wrote a little function based on the other answers here:

def pexec(*args):
    return subprocess.Popen(args, stdout=subprocess.PIPE).communicate()[0].rstrip()

Usage:

changeset = pexec('hg','id','--id')
branch = pexec('hg','id','--branch')
revnum = pexec('hg','id','--num')
print('%s : %s (%s)' % (revnum, changeset, branch))

Answer 2

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

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

Answer 3

subprocess.Popen: http://docs.python.org/2/library/subprocess.html#subprocess.Popen

import subprocess

command = "ntpq -p"  # the shell command
process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=None, shell=True)

#Launch the shell command:
output = process.communicate()

print output[0]

In the Popen constructor, if shell is True, you should pass the command as a string rather than as a sequence. Otherwise, just split the command into a list:

command = ["ntpq", "-p"]  # the shell command
process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=None)

If you need to read also the standard error, into the Popen initialization, you can set stderr to subprocess.PIPE or to subprocess.STDOUT:

import subprocess

command = "ntpq -p"  # the shell command
process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)

#Launch the shell command:
output, error = process.communicate()

Answer 4

This was perfect for me. You will get the return code, stdout and stderr in a tuple.

from subprocess import Popen, PIPE

def console(cmd):
    p = Popen(cmd, shell=True, stdout=PIPE)
    out, err = p.communicate()
    return (p.returncode, out, err)

For Example:

result = console('ls -l')
print 'returncode: %s' % result[0]
print 'output: %s' % result[1]
print 'error: %s' % result[2]

Answer 5

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 6

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.