who:tldr:7bd18

The command "who -a -H" is used in Linux/Unix systems to display information about the users currently logged in and their current activities.

Here's a breakdown of the command:

• "who" is a command that displays information about the users who are currently logged in.
• "-a" option tells the command to display all information available, including the login name, terminal, date and time of last activity, etc. This option shows both the active and idle users' sessions.
• "-H" option instructs the command to print column headers, providing a better view of the data's structure and making it easier to understand.

In summary, when you run the command "who -a -H", it shows all users who are logged in, their activities, and prints column headers for each field of information.