Which command can be used to see who is currently logged into the system?

The command that can be used to see who is currently logged into the system is "who." This command provides a list of all users currently logged in, along with relevant details such as their login time, terminal, and the originating IP address (if applicable). It offers a straightforward snapshot of logged-in users, making it useful for system administrators and users alike to monitor who is accessing the system at any given moment.

Other commands such as "whoami" are designed to show the username of the currently logged-in user running the command, rather than listing all logged-in users. The "users" command gives a simpler output that only lists the usernames of logged-in users, omitting additional information like login times or terminals. The "w" command does provide more comprehensive information about logged-in users, including their current activity, but it has a different focus as it details what each user is doing, rather than just listing them. Thus, while there are several commands that can relate to user sessions, "who" specifically fulfills the requirement of simply listing users currently logged into the system.