I just learned that if you hit and hold ESC while on the Mac Terminal, a prompt appears after a few seconds offering to show every command available on your system, including aliases, built-ins, and executables on your PATH.

Soruce: http://www.mactricksandtips.com/2008/05/list-all-possible-terminal-commands.html

However, the output is show through a more filter, and I cannot grep it or pipe it to another command.

Does anyone know how this magic output is generated? Is it just generated on the fly by Terminal? Is there a bash command that can be called explicitly on the command line and get the same result?

It is mostly curiosity, but I would love to be able to get the results as text I can post-process and not just browse on screen.