The vis command takes over your screen and shows the output of the initial ps command. Every 15 seconds, the command is executed again and your screen is updated with the new information. If this delay is too long for you, you can get vis to use a shorter delay using the -d option:
The information will now be updated every 2 seconds.
Your screen is cleared and you are shown the output of
On the top line,
tells you the command being run,
how long your delay is (if not the default), and how many times
it has been executed.
Command: ps Delay: 2 Exec: 1 PID TT STAT TIME COMMAND 2971 p1 S 0:06 -sh (csh) 6139 p1 S 0:00 vis -d 2 ps 6145 p1 R 0:00 ps 3401 q0 IW 0:13 -sh (csh) 5954 q0 S 0:01 vi ch01 14019 q5 IW 0:02 -sh (csh) 29380 r7 IW 0:00 -bin/csh (csh) 29401 rd IW 0:00 -bin/csh (csh)