os.setuid不会更改当前用户

Question

I wanted to change current user for script execution. I did this

import os
newuid = pwd.getpwnam('newuser').pw_uid
os.setuid(newuid)    
print('User :' + getpass.getuser());

I am still getting root . Is there better way than this? I want switch user once and then continue rest of the commands execution in the script with that new user.

Answer 1

getpass.getuser() doesn't use getuid() or geteuid() to get the current user.

http://docs.python.org/3/library/getpass.html#getpass.getuser

This function checks the environment variables LOGNAME, USER, LNAME and USERNAME, in order, and returns the value of the first one which is set to a non-empty string. If none are set, the login name from the password database is returned on systems which support the pwd module, otherwise, an exception is raised.

Answer 2

After trying modules os , subprocess , getpass , I realised that the problem is not whether the user is set. The user gets set or gets changed using os.setuid , however, the methods from modules to get username like os.getlogin() , getpass.getuser() , actually does not get username properly. If you run a shell command whoami or id using subprocess.Popen() or os.system() , you will get the changed user. These are little puzzled outputs for me. Below is script which shows all these weird behaviours.

import os
import subprocess
import pwd
import getpass

#os.chdir("/tmp")

#uid = pwd.getpwnam('newuser').pw_uid

os.setuid(500)     # newuser's id found from shell cmd line

print os.getuid()

p = subprocess.Popen(['id'], stdout=subprocess.PIPE, stderr=subprocess.PIPE)

out, err = p.communicate()

# print os.system('useradd newuser1') # Try this commenting, it will not create, and then  try commenting above line of setuid. i.e. it will become root, and then see the change.

# print os.getcwd()

print out,err

p = subprocess.Popen(['whoami'], stdout=subprocess.PIPE, stderr=subprocess.PIPE)

out, err = p.communicate()

print out,err

print getpass.getuser()

print os.getlogin()

print os.system('whoami')