Estimate file space usage.
The df command (short for disk free), is used to display information related to file systems about total space and available space.
List directory contents.
Send a signal to a process.
Display information about command type.
Define or display aliases.
Shows the full path of (shell) commands.
Xargs allows you to build and execute commands from standard input.
Tee command reads the standard input and writes it to both the standard output and one or more files.