OSX - Retrieve user id of logged-in user from a system service

Question

I'm writing a piece of software that runs as a system service in Mac OSX and cannot seem to find out how to get the 'active' user.

There appears to be APIs to iterate through the list of logged-in users and be able to tell from a value which one has the machine console... however I cannot find any documentation on these APIs.

Looking at /dev, it appears that the /dev/console device is owned by the currently logged-in user... however I have been unable to find any documentation to confirm this.

Any ideas?

Answer 1

You can use getuid and getgid to get the user's user id and group id. You can use getlogin or getlogin_r to retrieve a string representation of the current user's name. You can get additional user info with getpwuid.

As a side note, "man" is your friend. Whenever you're in doubt, consult the UNIX Manual Pages.

Answer 2

Answer courtesy of Apple's Technical Q&A

• Require SystemConfiguration.framework

  #include <SystemConfiguration/SystemConfiguration.h>
  /* .... */
  CFStringRef result = SCDynamicStoreCopyConsoleUser(NULL, NULL, NULL);
  /* .... */
  

OR use the utmpx APIs to get a list of all logged-in accounts from which you should be able to get the necessary information...