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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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KEYMAPS(5) File Formats Manual KEYMAPS(5)
keymaps - keyboard table descriptions for loadkeys and dumpkeys
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 (\).
A keymap can include other keymaps using the syntax
include "pathname"
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.
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 which 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
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.
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.
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.
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.
(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"
Andries Brouwer <[email protected]>
loadkeys(1), dumpkeys(1), showkey(1), xmodmap(1)
This page is part of the kbd (Linux keyboard tools) project.
Information about the project can be found at
⟨http://www.kbd-project.org/⟩. If you have a bug report for this
manual page, send it to [email protected]. This page was
obtained from the project's upstream Git repository
⟨https://github.com/legionus/kbd.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-07-01.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
kbd 24 April 1998 KEYMAPS(5)
Pages that refer to this page: dumpkeys(1), loadkeys(1), showkey(1)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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