.. link: http://dgplug.org/summertraining/2013/posts/thyarmageddon-user-finder-20130718-134348.html
.. description: 
.. tags: 
.. date: 2013/07/18 13:43:49
.. title: ThyArmageddon User Finder 20130718-134348
.. slug: thyarmageddon-user-finder-20130718-134348

User Finder Assignment
----------------------

This *User Finder* script_ will output the users on the current system.
When the user uses *useradd* to create a new user, *useradd* will use */etc/login.defs* to assign automatic UIDs
from the UID range specified in that configuration file. So the assumption is that the users will generally
not bother setting their own UID and let *useradd* handle it and their UID will be in the range.

Code
----

.. code:: python

        #!/usr/bin/env python
        """
        This script will output the users on the current system
        """
        
        from sys import exit
        from os import path
        from pwd import getpwall
        import re
        
        
        def print_users():
            """
            We get the information from passwd and the range of UIDs.
            Then we print all the users in the range.
            """
            passwd_info = getpwall()
        
            min_uid, max_uid = find_uid_range()
        
            print "Users on this system are:"
            print "-------------------------"
        
            for user in passwd_info:
                if (not user.pw_uid) or (user.pw_uid >= min_uid and user.pw_uid <= max_uid):
                    print user.pw_name
        
        
        def find_uid_range():
            """
            When a user uses useradd the system will assign a UID in the range
            mentioned in login.defs. So the assumption is that very rarely users
            choose their own UIDs and let the system choose instead. So we
            parse the login.defs file and get the values of UID_MIN and
            UID_MAX and return it as this is the range of UIDs autoassigned
            to users.
            """
            if path.exists("/etc/login.defs"):
                f = open("/etc/login.defs").read()
                min_uid_pattern = re.compile('\n\s*UID_MIN\s+(\d+)\s*\n')
                max_uid_pattern = re.compile('\n\s*UID_MAX\s+(\d+)\s*\n')
                min_uid = re.findall(min_uid_pattern, f)
                max_uid = re.findall(max_uid_pattern, f)
                return int(min_uid[0]), int(max_uid[0])
            else:
                print "Could not find login.defs file on system"
                exit(1)
        
        
        if __name__ == '__main__':
        
            print_users()
            exit(0)

.. _script: https://raw.github.com/ThyArmageddon/dgplug/master/userfinder/userfinder.py