Question

I am using the subprocess module and check_output() to create a virtual shell in my Python script, and it works fine for commands that return a zero exit status, however for ones that don’t it returns an exception without printing the error that would have been displayed in the output on a normal shell.

For instance, I would expect something to work like this:

>>> shell('cat non-existing-file')
cat: non-existing-file: No such file or directory

But instead, this happens:

>>> shell('cat non-existing-file')
CalledProcessError: Command 'cat non-existing-file' returned non-zero exit status 1 (file "/usr/lib/python2.7/subprocess.py", line 544, in check_output)

Even though I could remove the Python exception message using try and except, I still want the cat: non-existing-file: No such file or directory to display to the user.

How would I go about doing this?

shell():

def shell(command):
    output   = subprocess.check_output(command, shell=True)
    finished = output.split('\n')

    for line in finished:
      print line
    return

Answer 1

Something like this perhaps?

def shell(command):
    try:
        output = subprocess.check_output(command, shell=True, stderr=subprocess.STDOUT)
    except Exception, e:
        output = str(e.output)
    finished = output.split('\n')
    for line in finished:
        print line
    return