There are to commands that might help finding the commands you are looking for.
man:
man -k "logged on"
Result:
w (1) - Show who is logged on and what they are doing
who (1) - show who is logged on
apropos:
apropos "logged in"
Result:
last (1) - show listing of last logged in users
lastb [last] (1) - show listing of last logged in users
users (1) - print the user names of users currently logged in to the current host