In Unix, how do I check who else is logged into the same computer as I am?

You can use any one of several Unix commands to see who is logged into the same computer as you. Each command yields different amounts of information:

You can obtain a list of information about current users by entering the finger command with no options:   

finger 

For a list of usernames currently logged in, presented in a condensed, single-line format, enter:  

users

For more information, including each login of a username, the terminal users are attached to, the date and time that login began, and possibly the computer from which they are making the connection, enter:  

who

For extensive information, including username, terminal, IP number of the source computer, the time the login began, any idle time, process CPU cycles, job CPU cycles, and the currently running command, enter:

w