How do I get the name of the active user via the command line in OS X?

Question

How do I get the name of the active user via the command line in OS X?

Answer 1

If you want to know who's currently logged in to the system:

$ w
 15:56:14 up 5 days, 20:58,  6 users,  load average: 0.43, 0.53, 0.50
USER     TTY        LOGIN@   IDLE   JCPU   PCPU WHAT
me       pts/2     Fri19    1:03m  0.98s  0.98s -/bin/bash
me       pts/3     09:55    6:00m  0.43s  0.43s /bin/bash
me       pts/5     15:56    0.00s  0.23s  0.00s w

(This is from a Linux system; the formatting on OS X may be slightly different, but the information should be about the same.)

There may be multiple login sessions; UNIX is designed to be a multi-user system, after all.