To find out who is logged on to the system:
who erco02 ttyPt Nov 3 08:01 (braid.ucs:0.0) fran ttyPu Oct 26 11:23 (dirac.maths.ed.a) calvin ttyPv Nov 5 09:07 (hobbes.ucs.ed.ac) djs ttyPx Nov 5 11:39 (126.96.36.199) aipex ttyPB Nov 5 11:41 (owl.dai.ed.ac.uk) harvey ttyPF Nov 5 09:12 (rabbit.warren.ed)
This displays the name of the user, the date and time that they logged on and the name of their terminal.
Notice that a user might have been logged on for several days or even weeks.
To find out who is logged on and prevent the information from rolling off the screen:
who | more
This sends the output from the who command through another program known as a pager which presents the information a page at a time.