Calling Shell from Python

Things on this page are fragmentary and immature notes/thoughts of the author. Please read with your own judgement!

1. subprocess.run is preferred to the function os.system for invoking shell commands. For more discussions, pleaser refer to [Hands on the Python module subprocess]https://www.legendu.net/en/blog/hands-on-the-python-model-subprocess .

2. There are multiple ways to feed input to a shell command programmatically instead of interactively via stdin.

   1. Pipe is used to feed the output (text) of a shell command as the input to another shell command. What if you have something that is not the output a shell command? A simple trick is to echo it and feed it to the shell command. The command below is an example of feeding password to the shell command kinit.

       :::bash
       echo 'your_password' | kinit

   2. The above trick can be used both for os.system and subprocess.run (with shell=True). However, subprocess.run has an better built-in support to feed input to a shell command via the input parameter.

       :::python
       subprocess.run(["kinit"], input=b"your_password")

   3. pexpect

shlex¶

Parsing Shell commands.

References¶

https://docs.python.org/3/library/subprocess.html