The Linux keyboard and console HOWTO: Examples of use of loadkeys and xmodmap

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## 15. Examples of use of loadkeys and xmodmap

Switching Caps Lock and Control on the keyboard (assuming you use keymaps 0-15; check with `dumpkeys | head -1`)

> `

>             % loadkeys
>             keymaps 0-15
>             keycode 58 = Control
>             keycode 29 = Caps_Lock
>             %

> `

Switching them under X only:

> `

>             % xmodmap .xmodmaprc

> `

where `.xmodmaprc` contains lines

> `

>             remove Lock = Caps_Lock
>             remove Control = Control_L
>             keysym Control_L = Caps_Lock
>             keysym Caps_Lock = Control_L
>             add Lock = Caps_Lock
>             add Control = Control_L

> `

What is this about the key numbering? Backspace is 14 under Linux, 22 under X? Well, the numbering can best be regarded as arbitrary; the Linux number of a key can be found using showkey(1), and the X number using xev(1). Often the X number will be 8 more than the Linux number.

Something else people like to change are the bindings of the function keys. Suppose that you want to make F12 produce the string "emacs ". Then

> `

>             % loadkeys
>             keycode 88 = F12
>             string F12 = "emacs "
>             %

> `

will do this. More explicitly, the procedure is like this: (i) find the keycodes of the keys to be remapped, using showkey(1). (ii) save the current keymap, make a copy and edit that:

> `

>             % dumpkeys > my_keymap
>             % cp my_keymap trial_keymap
>             % emacs trial_keymap
>             % loadkeys trial_keymap
>             %

> `

The format of the table can be guessed by looking at the output of `dumpkeys`, and is documented in keymaps(5). When the new keymap functions as desired, you can put an invocation

> `

>             loadkeys my_new_keymap

> `

in `/etc/rc.local` or so, to execute it automatically at boot-up. Note that changing modifier keys is tricky, and a newbie can easily get into a situation only an expert can get out of.

The default directory for keymaps is `/usr/lib/kbd/keymaps`. The default extension for keymaps is `.map`. For example, `loadkeys uk` would probably load `/usr/lib/kbd/keymaps/i386/qwerty/uk.map`. (With kbd-0.95 and older this would be `/usr/lib/kbd/keytables` and `/usr/lib/kbd/keytables/uk.map`.)

(On my machine) `/dev/console` is a symbolic link to `/dev/tty0`, and the kernel regards `/dev/tty0` as a synonym for the current VT. XFree86 1.3 changes the owner of `/dev/tty0`, but does not reset this after finishing. Thus, `loadkeys` or `dumpkeys` might fail because someone else owns `/dev/tty0`; in such a case you might run X first. Note that you cannot change keyboard mappings when not at the console (and not superuser).

## 15.1 `I can use only one finger to type with'

"Can the Shift, Ctrl and Alt keys be made to behave as toggles?"

Yes, after saying

> `

>             % loadkeys
>             keymaps 0-15
>             keycode 29 = Control_Lock
>             keycode 42 = Shift_Lock
>             keycode 56 = Alt_Lock
>             %

> `

the left Control, Shift and Alt keys will act as toggles. The numbers involved are revealed by showkey (and usually are 29, 97, 42, 54, 56, 100 for left and right control, shift and alt, respectively), and the functions are Control_Lock, Shift_Lock, Alt_Lock, ALtGr_Lock.

"What about `sticky' modifier keys?"

Since version 1.3.33, the kernel knows about `sticky' modifier keys. These act on the next key pressed. So, where one earlier needed the 3-symbol sequence Shift_Lock a Shift_Lock to type `A', one can now use the 2-symbol sequence SShift_Lock a. Versions of the kbd package older than 0.93 do not yet include code for these sticky modifiers, and have to invoke them using their hexadecimal codes. For example,

> `

>             % loadkeys
>             keymaps 0-15
>             keycode 54 = 0x0c00
>             keycode 97 = 0x0c02
>             keycode 100 = 0x0c03
>             %

> `

will make the right Shift, Ctrl, Alt sticky versions of the left ones. From 0.93 on you can say

> `

>             % loadkeys
>             keymaps 0-15
>             keycode 54 = SShift
>             keycode 97 = SCtrl
>             keycode 100 = SAlt
>             %

> `

to obtain the same result. This will allow you to type Ctrl-Alt-Del in three keystrokes with one hand.

The keymaps line in these examples should cover all keymaps you have in use. You find what keymaps you have in use by

> `

>             % dumpkeys | head -1

> `

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