Unix Power Tools, 3rd Edition

Chapter 6. Your X Environment

Defining Keys and Button Presses with xmodmap

If you have a Linux system, you may want to use loadkeys instead of xmodmap. loadkeys is designed to set the keymap used by the system as a whole, particularly the console, so use your own judgment. Whatever is done in xmodmap will affect X but not the system console.

An important piece to the X Window System puzzle is filled by the xmodmap client. When the user performs any action — such as typing a key or moving the mouse — the server sends a packet of information to the client called an event. These events are then translated into actions by the client. You can use the xmodmap utility to effectively change the event that is reported to the client.

Keysym mappings are mappings of keyboard events at the server level, before the event is sent to the client. Keysyms are the symbols used for each key on the keyboard.

The X server maintains a keymap table , which contains a listing of keys on the keyboard and how they should be interpreted. A client gets the keymap table from the server upon client startup. In most cases, the keymap table is used to interpret keys literally — when you press the letter “a,” a key code is sent to the client that corresponds to the letter “a” in the keymap table.

You can use the xmodmap client to reassign key codes within the keymap table. xmodmap can therefore be used to redefine how the key is interpreted by the client. You probably wouldn’t want to translate the alphanumeric ...