w:tldr:4bc4d

The command "w ${username}" is used to display information about the users currently logged into a system.

Here's a breakdown of the command:

• "w" - It is a built-in command in Unix-like operating systems that stands for "who" and provides information about the logged-in users.
• "${username}" - This is a variable placeholder that should be replaced with the actual username you want to check. For example, if you want to know about the user "john", you would replace "${username}" with "john" in the command.

So, when you execute the command "w ${username}", it will show information about the user you specified, such as their username, terminal or session they are logged in, login time, idle time, and the command they are currently running.