Runs an external command in Python and returns exit code, stdout and stderr contents.

runcommand.py

# runcommand.py
# Handy function that executes an external command in the shell
# and returns 3 values: exit code of the command, its standard output
# and its error output.
# If you run the script directly, an example is provided:
# first it will run a successful command and then one with errors
# (you may want to modify them if not running a Unix system).

import subprocess

def runcommand (cmd):
    proc = subprocess.Popen(cmd,
                            stdout=subprocess.PIPE,
                            stderr=subprocess.PIPE,
                            shell=True,
                            universal_newlines=True)
    std_out, std_err = proc.communicate()
    return proc.returncode, std_out, std_err

def main():
    print("==================================================");
    print('Running "ls -lh"...');
    print("==================================================");
    code, out, err = runcommand("ls -lh");
    print("Return code: {}".format(code));
    print("--------------------------------------------------");
    print("stdout:");
    print(out);
    print("--------------------------------------------------");
    print("stderr:");
    print(err);
    print("--------------------------------------------------");

    print("==================================================");
    print('Running "ls -lj"...');
    print("==================================================");
    code, out, err = runcommand("ls -lj");
    print("Return code: {}".format(code));
    print("--------------------------------------------------");
    print("stdout:");
    print(out);
    print("--------------------------------------------------");
    print("stderr:");
    print(err);
    print("--------------------------------------------------");
    
if __name__ == '__main__':
    main()