THE META KEY

THE META KEY

If you venture into the Readline documentation, which can be found in the “READLINE” section of the bash man page, you will encounter the term meta key. On modern keyboards this maps to the ALT key, but it wasn’t always so.
Back in the dim times (before PCs but after Unix) not everybody had their own computer. What they might have had was a device called a terminal. A ter minal was a communication device that featured a text-display screen and a keyboard and had just enough electronics inside to display text characters and move the cursor around. It was attached (usually by serial cable) to a larger computer or the communication network of a larger computer. There were many different brands of terminals, and they all had different keyboards and display feature sets. Since they all tended to at least understand ASCII, software developers wanting portable applications wrote to the lowest common denom inator. Unix systems have a very elaborate way of dealing with terminals and their different display features. Since the developers of Readline could not be sure of the presence of a dedicated extra control key, they invented one and called it meta. While the ALT key serves as the meta key on modern keyboards, you can also press and release the ESC key to get the same effect as holding down the ALT key if you’re still using a terminal (which you can still do in Linux!).