xmodmap command_examples

xmodmap – utility for modifying keymaps and pointer button mappings in X

Many pointers are designed such that the first button is pressed using the index finger of the right hand. People who are left-handed frequently find that it is more comfortable to reverse the button codes that  get generated so that the primary button is pressed using the index finger of the left hand. This could be done on a 3 button pointer as follows:

% xmodmap -e "pointer = 3 2 1"

Many applications support the notion of Meta keys (similar to Control keys except that Meta is held down instead of Control). However, some servers do not have a Meta keysym in the default keymap table, so one needs to be added by hand. The following command will attach Meta to the Multi-language key (sometimes labeled Compose Character). It also takes advantage of the fact that applications that need a Meta key simply need to get the keycode and don’t require the keysym to be in the first column of the keymap table. This means that applications that are looking for a Multi_key (including the default modifier map) won’t notice any change.

% xmodmap -e "keysym Multi_key = Multi_key Meta_L"

Similarly, some keyboards have an Alt key but no Meta key. In that case the following may be useful:

% xmodmap -e "keysym Alt_L = Meta_L Alt_L"

One of the more simple, yet convenient, uses of xmodmap is to set the keyboard’s “rubout” key to generate an alternate keysym. This frequently involves exchanging Backspace with Delete to be more comfortable to the user. If the ttyModes resource in xterm is set as well, all terminal emulator windows will use the same key for erasing characters:

% xmodmap -e "keysym BackSpace = Delete"
% echo "XTerm*ttyModes: erase ^?" | xrdb -merge

Some keyboards do not automatically generate less than and greater than characters when the comma and period keys are shifted. This can be remedied with xmodmap by resetting the bindings for the comma and period with the following scripts:

!
! make shift-, be
!
keysym comma = comma less
keysym period = period greater

One of the more irritating differences between keyboards is the location of the Control and CapsLock keys. A common use of xmodmap is to swap these two keys as follows:

!
! Swap Caps_Lock and Control_L
!
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

This example can be run again to swap the keys back to their previous assignments.

The keycode command is useful for assigning the same keysym to multiple keycodes. Although unportable, it also makes it possible to write scripts that can reset the keyboard to a known state. The following script sets the backspace key to generate Delete (as shown above), flushes all existing caps lock bindings, makes the CapsLock key be a control key, make F5 generate Escape, and makes Break/Reset be a shift lock.

!
! On the HP, the following keycodes have key caps as listed:
!
! 101 Backspace
! 55 Caps
! 14 Ctrl
! 15 Break/Reset
! 86 Stop
! 89 F5
!
keycode 101 = Delete
keycode 55 = Control_R
clear Lock
add Control = Control_R
keycode 89 = Escape
keycode 15 = Caps_Lock
add Lock = Caps_Lock