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         


        

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

Use ckeck_output method of subprocess

import subprocess
address = 192.168.x.x
res = subprocess.check_output(['ping', address, '-c', '3'])

Finally parse the string

for line in res.splitlines():

Hope it helps, happy coding

Answer 3

for Python 2.7+ the idiomatic answer is to use subprocess.check_output()

You should also note the handling of arguments when invoking a subprocess, as it can be a little confusing....

If args is just single command with no args of its own (or you have shell=True set), it can be a string. Otherwise it must be a list.

for example... to invoke the ls command, this is fine:

from subprocess import check_call
check_call('ls')

so is this:

from subprocess import check_call
check_call(['ls',])

however, if you want to pass some args to the shell command, you can't do this:

from subprocess import check_call
check_call('ls -al')

instead, you must pass it as a list:

from subprocess import check_call
check_call(['ls', '-al'])

the shlex.split() function can sometimes be useful to split a string into shell-like syntax before creating a subprocesses... like this:

from subprocess import check_call
import shlex
check_call(shlex.split('ls -al'))

Answer 4

The following captures stdout and stderr of the process in a single variable. It is Python 2 and 3 compatible:

from subprocess import check_output, CalledProcessError, STDOUT

command = ["ls", "-l"]
try:
    output = check_output(command, stderr=STDOUT).decode()
    success = True 
except CalledProcessError as e:
    output = e.output.decode()
    success = False

If your command is a string rather than an array, prefix this with:

import shlex
command = shlex.split(command)

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

This works perfectly for me:

import subprocess
try:
    #prints results and merges stdout and std
    result = subprocess.check_output("echo %USERNAME%", stderr=subprocess.STDOUT, shell=True)
    print result
    #causes error and merges stdout and stderr
    result = subprocess.check_output("copy testfds", stderr=subprocess.STDOUT, shell=True)
except subprocess.CalledProcessError, ex: # error code <> 0 
    print "--------error------"
    print ex.cmd
    print ex.message
    print ex.returncode
    print ex.output # contains stdout and stderr together