====== system / popen / exec ======

In general: run system commands.

Current recommended way is to use [[https://docs.python.org/3/library/subprocess.html|subprocess]] module. This module intends to **replace several older** modules and functions:
<code python>
os.system
os.spawn*
</code>

[[https://docs.python.org/3/library/subprocess.html#replacing-older-functions-with-the-subprocess-module|Replacing Older Functions with the subprocess Module]]

[[https://docs.python.org/3/library/subprocess.html#replacing-os-system|Replacing os.system()]]

Features:
  * possible to execute in shell:
    * all command and params can be specified as string not list
    * multiple commands can be executed at once; shell pipes usage possible
  * configurable check for return codes or output

Parameters:
  * [[https://docs.python.org/3.10/library/io.html#io-text-encoding|io-text-encoding]]
  * 

Examples:

<code python>
def run_command(cmd):
    output = Popen(cmd, stdout=PIPE)
    return output.communicate()[0].decode("utf-8").split("\n")
</code>    

see [[programming:python:lib:contextlib]] to catch other components stdout/stderr.

<code python>
import subprocess
meta_data = subprocess.check_output(['netsh', 'wlan', 'show', 'profiles'])
data = meta_data.decode('utf-8', errors ="backslashreplace")
</code>

<code python>
return subprocess.check_output(
                [self.FW_PRINTENV, '-n', var],
                stderr=subprocess.STDOUT, encoding='ascii').strip()
...                
return subprocess.check_call([self.FW_SETENV, var, value])                
</code>