Ubuntu Manpage: keymaps - keyboard table descriptions for loadkeys and dumpkeys

Provided by: kbd_2.3.0-3ubuntu4.22.04_amd64

NAME

       keymaps - keyboard table descriptions for loadkeys and dumpkeys

DESCRIPTION

       These  files  are  used by loadkeys(1) to modify the translation tables used by the kernel
       keyboard driver and generated by dumpkeys(1) from those translation tables.

       The format of these files is vaguely similar to the one accepted by xmodmap(1).  The  file
       consists of charset or key or string definition lines interspersed with comments.

       Comments  are  introduced  with  !   or  # characters and continue to the end of the line.
       Anything following one of these characters on that line is  ignored.  Note  that  comments
       need not begin from column one as with xmodmap(1).

       The  syntax  of  keymap files is line oriented; a complete definition must fit on a single
       logical line. Logical lines can, however, be split into multiple physical lines by  ending
       each subline with the backslash character (\).

INCLUDE FILES

       A keymap can include other keymaps using the syntax

              include "pathname"

CHARSET DEFINITIONS

       A character set definition line is of the form:

              charset "iso-8859-x"

       It  defines  how  following keysyms are to be interpreted.  For example, in iso-8859-1 the
       symbol mu (or micro) has code 0265, while in iso-8859-7 the letter mu has code 0354.

COMPLETE KEYCODE DEFINITIONS

Each complete key definition line is of the form:

keycode keynumber = keysym keysym keysym...

keynumber is the internal identification number of the key, roughly equivalent to the scan
code of it. keynumber can be given in decimal, octal or hexadecimal notation. Octal is
denoted by a leading zero and hexadecimal by the prefix 0x.

Each of the keysyms represent keyboard actions, of which up to 256 can be bound to a
single key. The actions available include outputting character codes or character
sequences, switching consoles or keymaps, booting the machine etc. (The complete list can
be obtained from dumpkeys(1) by saying dumpkeys -l .)

Each keysym may be prefixed by a '+' (plus sign), in wich case this keysym is treated as a
"letter" and therefore affected by the "CapsLock" the same way as by "Shift" (to be
correct, the CapsLock inverts the Shift state). The ASCII letters ('a'-'z' and 'A'-'Z')
are made CapsLock'able by default. If Shift+CapsLock should not produce a lower case
symbol, put lines like

keycode 30 = +a A

in the map file.

Which of the actions bound to a given key is taken when it is pressed depends on what
modifiers are in effect at that moment. The keyboard driver supports 9 modifiers. These
modifiers are labeled (completely arbitrarily) Shift, AltGr, Control, Alt, ShiftL, ShiftR,
CtrlL, CtrlR and CapsShift. Each of these modifiers has an associated weight of power of
two according to the following table:

modifier weight

Shift 1
AltGr 2
Control 4
Alt 8
ShiftL 16
ShiftR 32
CtrlL 64
CtrlR 128
CapsShift 256

The effective action of a key is found out by adding up the weights of all the modifiers
in effect. By default, no modifiers are in effect, so action number zero, i.e. the one in
the first column in a key definition line, is taken when the key is pressed or released.
When e.g. Shift and Alt modifiers are in effect, action number nine (from the 10th column)
is the effective one.

Changing the state of what modifiers are in effect can be achieved by binding appropriate
key actions to desired keys. For example, binding the symbol Shift to a key sets the Shift
modifier in effect when that key is pressed and cancels the effect of that modifier when
the key is released. Binding AltGr_Lock to a key sets AltGr in effect when the key is
pressed and cancels the effect when the key is pressed again. (By default Shift, AltGr,
Control and Alt are bound to the keys that bear a similar label; AltGr may denote the
right Alt key.)

Note that you should be very careful when binding the modifier keys, otherwise you can end
up with an unusable keyboard mapping. If you for example define a key to have Control in
its first column and leave the rest of the columns to be VoidSymbols, you're in trouble.
This is because pressing the key puts Control modifier in effect and the following actions
are looked up from the fifth column (see the table above). So, when you release the key,
the action from the fifth column is taken. It has VoidSymbol in it, so nothing happens.
This means that the Control modifier is still in effect, although you have released the
key. Re-pressing and releasing the key has no effect. To avoid this, you should always
define all the columns to have the same modifier symbol. There is a handy short-hand
notation for this, see below.

keysyms can be given in decimal, octal, hexadecimal, unicode or symbolic notation. The
numeric notations use the same format as with keynumber. Unicode notation is "U+"
followed by four hexadecimal digits. The symbolic notation resembles that used by
xmodmap(1). Notable differences are the number symbols. The numeric symbols '0', ..., '9'
of xmodmap(1) are replaced with the corresponding words 'zero', 'one', ... 'nine' to avoid
confusion with the numeric notation.

It should be noted that using numeric notation for the keysyms is highly unportable as the
key action numbers may vary from one kernel version to another and the use of numeric
notations is thus strongly discouraged. They are intended to be used only when you know
there is a supported keyboard action in your kernel for which your current version of
loadkeys(1) has no symbolic name.

There is a number of short-hand notations to add readability and reduce typing work and
the probability of typing-errors.

First of all, you can give a map specification line, of the form

keymaps 0-2,4-5,8,12

to indicate that the lines of the keymap will not specify all 256 columns, but only the
indicated ones. (In the example: only the plain, Shift, AltGr, Control, Control+Shift, Alt
and Control+Alt maps, that is, 7 columns instead of 256.) When no such line is given, the
keymaps 0-M will be defined, where M+1 is the maximum number of entries found in any
definition line.

Next, you can leave off any trailing VoidSymbol entries from a key definition line.
VoidSymbol denotes a keyboard action which produces no output and has no other effects
either. For example, to define key number 30 to output 'a' unshifted, 'A' when pressed
with Shift and do nothing when pressed with AltGr or other modifiers, you can write

keycode 30 = a A

instead of the more verbose

keycode 30 = a A VoidSymbol VoidSymbol \
VoidSymbol VoidSymbol VoidSymbol ...

For added convenience, you can usually get off with still more terse definitions. If you
enter a key definition line with only and exactly one action code after the equals sign,
it has a special meaning. If the code (numeric or symbolic) is not an ASCII letter, it
means the code is implicitly replicated through all columns being defined. If, on the
other hand, the action code is an ASCII character in the range 'a', ..., 'z' or 'A', ...,
'Z' in the ASCII collating sequence, the following definitions are made for the different
modifier combinations, provided these are actually being defined. (The table lists the
two possible cases: either the single action code is a lower case letter, denoted by 'x'
or an upper case letter, denoted by 'Y'.)

modifier symbol

none x Y
Shift X y
AltGr x Y
Shift+AltGr X y
Control Control_x Control_y
Shift+Control Control_x Control_y
AltGr+Control Control_x Control_y
Shift+AltGr+Control Control_x Control_y
Alt Meta_x Meta_Y
Shift+Alt Meta_X Meta_y
AltGr+Alt Meta_x Meta_Y
Shift+AltGr+Alt Meta_X Meta_y
Control+Alt Meta_Control_x Meta_Control_y
Shift+Control+Alt Meta_Control_x Meta_Control_y
AltGr+Control+Alt Meta_Control_x Meta_Control_y
Shift+AltGr+Control+Alt Meta_Control_x Meta_Control_y

SINGLE MODIFIER DEFINITIONS

       All the previous forms of key definition lines always define all the M+1 possible modifier
       combinations being defined, whether the line actually contains that many action  codes  or
       not.   There  is,  however,  a variation of the definition syntax for defining only single
       actions to a particular modifier combination of a key. This is especially useful,  if  you
       load  a  keymap  which  doesn't  match your needs in only some modifier combinations, like
       AltGr+function keys. You can then make a small local file redefining only  those  modifier
       combinations and loading it after the main file.  The syntax of this form is:

       { plain | <modifier sequence> } keycode keynumber = keysym

       , e.g.,
              plain keycode 14 = BackSpace
              control alt keycode 83 = Boot
              alt keycode 105 = Decr_Console
              alt keycode 106 = Incr_Console
       Using  "plain" will define only the base entry of a key (i.e. the one with no modifiers in
       effect) without affecting the bindings of other modifier combinations of that key.

STRING DEFINITIONS

       In addition to comments and key definition lines, a keymap can contain string definitions.
       These  are  used  to define what each function key action code sends. The syntax of string
       definitions is:

              string keysym = "text"

       text can contain literal characters, octal character codes  in  the  format  of  backslash
       followed  by  up to three octal digits, and the three escape sequences \n, \\, and \", for
       newline, backslash and quote, respectively.

COMPOSE DEFINITIONS

       Then there may also be compose definitions. They have syntax

              compose 'char' 'char' to 'char'
       and describe how two bytes are combined to form a third one (when a dead accent or compose
       key is used).  This is used to get accented letters and the like on a standard keyboard.

ABBREVIATIONS

       Various abbreviations can be used with kbd-0.96 and later.

       strings as usual
              Defines the usual values of the strings (but not the keys they are bound to).

       compose as usual for "iso-8859-1"
              Defines the usual compose combinations.

       To find out what keysyms there are available for use in keymaps, use the command

              dumpkeys --long-info

       Unfortunately,  there  is  currently no description of what each symbol does. It has to be
       guessed from the name or figured out from the kernel sources.

EXAMPLES

       (Be careful to use a keymaps line, like the first line of `dumpkeys`, or "keymaps 0-15" or
       so.)

       The following entry exchanges the left Control key and the Caps Lock key on the keyboard:

              keycode  58 = Control
              keycode  29 = Caps_Lock

       Key  number  58  is  normally the Caps Lock key, and key number 29 is normally the Control
       key.

       The following entry sets the Shift and Caps Lock keys to behave more nicely, like in older
       typewriters.  That  is,  pressing Caps Lock key once or more sets the keyboard in CapsLock
       state and pressing either of the Shift keys releases it.

              keycode  42 = Uncaps_Shift
              keycode  54 = Uncaps_Shift
              keycode  58 = Caps_On

       The following entry sets the layout of the edit pad in the enhanced keyboard  to  be  more
       like that in the VT200 series terminals:

              keycode 102 = Insert
              keycode 104 = Remove
              keycode 107 = Prior
              shift keycode 107 = Scroll_Backward
              keycode 110 = Find
              keycode 111 = Select
              control alt   keycode 111 = Boot
              control altgr keycode 111 = Boot

       Here's  an  example  to  bind the string "du\ndf\n" to the key AltGr-D. We use the "spare"
       action code F100 not normally bound to any key.

              altgr keycode 32 = F100
              string F100 = "du\ndf\n"