The w command shows who is logged on and what they are doing.

The header shows: current time, how long the system has been running, how many users are currently logged on, and the load averages for the past 1, 5, and 15 minutes.

Entries for each user: login name, tty name, remote host, login time, idle time, JCPU, PCPU, command line of current process.

JCPU: time used by all processes attached to the tty (includes currently running background jobs).

PCPU: time used by current process (ie. the one named in the "what" field).

-h     doesn't print the header
-s     short format - doesn't print login time, JCPU, or PCPU.
-f     prints the "remote host name" field.
users  shows information on named users


lager 8:45pm {0}[~] w
  5:50pm    up 4 days, 8:51,  42 users,  load average: 0.41, 0.26, 0.20
User        tty    login@   idle    JCPU    PCPU    what
wsitch    ttyp0   Mon11am   1:17                    -tcsh
adevries  ttyp2    1:08pm      4                    -
wsitch    ttyp6    8:06pm     36      17            tin
cb        ttypa    8:12pm                           pine
adevries  ttypb    8:36pm   1:10       1       1    lynx
kmwood    ttyrl    8:39pm     17                    ftp