Unix Command - who

The Unix command who displays a list of users who are currently logged into a computer. The command accepts various options that vary by system to further specify the information that is returned, such as the length of time a particular user has been connected or what pseudo-teletype a user is connected to. The who command is related to the command w, which provides the same information but also displays additional data and statistics.

Example output 
user11    pts/35       Apr 18 08:40    (localhost)
user12    pts/27       Apr 18 09:50    (localhost)