13.8.1 Who Is Doing What: w

With the command w, find out who is logged onto the system and what each user is doing. For example:

tester@linux:~> w
 16:33:03 up  3:33,  2 users,  load average: 0.14, 0.06, 0.02
USER     TTY        LOGIN@   IDLE   JCPU   PCPU WHAT
tester   :0        16:33   ?xdm?   9.42s  0.15s /bin/sh /opt/kde3/bin/startk
tester   pts/0     15:59    0.00s  0.19s  0.00s w
   

If any users of other systems have logged in remotely, the parameter -f shows the computers from which they have established the connection.