How to determine what user and group a Python script is running as?

Question

I have a CGI script that is getting an \"IOError: [Errno 13] Permission denied\" error in the stack trace in the web server\'s error log.

As part of deb

Answer 1

import os, getpass
print getpass.getuser()

Consider the following script.

---- foo.py ---- 
import os, getpass
print "Env thinks the user is [%s]" % (os.getlogin());
print "Effective user is [%s]" % (getpass.getuser());

Consider running the script.

$ python ./foo.py

results in

Env thinks the user is [jds]
Effective user is [jds]

now run

$ sudo -u apache python ./foo.py

results in

Env thinks the user is [jds]
Effective user is [apache]

As you can see, you these 2 calls os.getlogin() and getpass.getuser() are not the same thing. The underlying principle is how linux/and other unix's manages the running user.

Consider

$ id -u

1000

vs the effective id of the running process.

$ sudo -u apache id -u

33

Note: this is exactly what web servers are doing when they start up. They are creating a sandbox (by forking/divorcing the psudo terminal etc), and running as another user. For an in-depth account of what is going on here: see the chapter on 'daemon processes' in the Advanced Programming in the UNIX environment book.

Another good thread on the subject.