The “who” command lets you display the users that are currently logged into your Unix computer system.
This is the basic who command with no command-line arguments. It shows the names of users that are currently logged in, and may also show the terminal they’re logged in on, and the time they logged in.
who | more
In this example the output of the who command is piped into the more command. This is useful when there are a lot of users logged into your computer system, and part of the output of the who command scrolls off the screen. See the more command for more examples.
who -a The -a argument lists all available output of the who command for each user To find out how many users are logged on, type
% who | wc -l