Running Python script as root (with sudo) - what is the username of the effective user?

Question

I've recently began using ConfigParser() for my python scripts to add some functionality to them for config files. I know how to use it but I have a problem. My script needs to run as the root user, using sudo. The config files are in ~/.config/scriptconfig/ but when you run a script as sudo it temporarily changes users to root, so it doesn't find the config files. What I want to do is get the config file of the effective user so it grabs /home/myuser/.config/scriptconfig/config.cfg instead of /root/.config/scriptconfig/config.cfg, which doesn't exist.

I need the script to be able to run on different machines, not just mine. So I need to get the home directory of the effective user

Here is an example of the code I'm trying to use:

import os, ConfigParser
config = ConfigParser.RawConfigParser()
homepath = os.path.expanduser("~/")
configpath = homepath + ".config/scriptconfig/config.cfg"
config.read(configpath)
get = config.get('Config', 'Example')
print get

It should print the value of example from the config file but when ran as sudo, the path is /home/root so it doesn't find the config file.

Answer 1

If you run your script with sudo (sudo myscript.py) then the environment variable $USER will be root and the environment variable $SUDO_USER will be the name of the user who executed the command sudo myscript.py. This following is simply a clarification of the previous post by Cédric Julien. Consider the following scenario:

A linux user bob is logged into the system and possesses sudo privileges. He writes the following python script named myscript.py:

    #!/usr/bin/python
    import os
    print os.getenv("USER")
    print os.getenv("SUDO_USER")

He then makes the script executable with chmod +x myscript.py and then executes his script with sudo privileges with the command:

sudo ./myscript.py

The output of that program will be (using python 2.x.x):

    root
    bob

If bob runs the program sans sudo privileges with

./myscript.py

he will get the following output:

    bob
    None