How to use string variable in subprocess.check_output in python

Question

I want to run a command having args on linux using python

i have wriiten following code:

import subprocess

msg = 'this is commit'
cmdtorun = 'hg commit -m "{}"'.format(msg)

try:
    subprocess.check_output(cmdtorun, shell=True)
    print "commit done"
except subprocess.CalledProcessError:
    print "commit failed

but this is giving me error.

Answer 1

Most likely, your problem is something else entirely. Check what error you actually get. I'm guessing that you're executing hg in the wrong directory (pass in the cwd= keyword argument).

Also, your escaping with '"{}"'.format is incorrect - it fails when msg contains a double quote. You could escape with shlex.quote , but that's error-prone. It's far easier to let subprocess do the escaping:

import subprocess
msg = 'this is commit'
try:
    subprocess.check_output(['hg', 'commit', '-m', msg])
    print("commit done")
except subprocess.CalledProcessError as cpe:
    print("commit failed: %r" % cpe)