Python:Process

lastmod 2016-01-24created 2015-03-015 edits

Notes on running processes.

os.system

import os
import sys
os.system ('ls -al | grep "user")

The return value indicates whether the command ran successfully.

subprocess

If the goal is just execution, as with os.system, use subprocess.call as shown below.

import subprocess

subprocess.call ('ls -al', shell=True)

To use the printed stdout output, use subprocess.check_output.

import subprocess

result = subprocess.check_output('./program' , shell=True)
if result == 'AAA' :
    print "123"
elif result == 'BBB' :
    print "456"

STDERR can be obtained as follows.

from subprocess import Popen, PIPE, STDOUT

cmd = 'ls /etc/fstab /etc/non-existent-file'
p = Popen(cmd, shell=True, stdin=PIPE, stdout=PIPE, stderr=STDOUT, close_fds=True)
output = p.stdout.read()
print output

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