su:tldr:44b7c

The command "su ${username}" is used in Linux and Unix-based systems to switch to a different user account. Here's how it works:

• "su" stands for "substitute user" and it allows you to temporarily change to another user account without logging out of the current account. It is often used to gain root or administrative privileges.
• "${username}" is a placeholder that represents the username you want to switch to. You need to replace it with the actual username you want to use. For example, if you want to switch to the user "john", the command would be "su john".

When you run the "su ${username}" command, you will be prompted for the password of the user account you want to switch to. Once you enter the correct password, you will be logged in as that user and can work with the privileges and permissions associated with that account.