LDP
/
old-www
1
1
Fork 0
Code Issues Pull Requests Releases Wiki Activity
old-www/HOWTO/text/Keyboard-and-Console-HOWTO

2120 lines
74 KiB
Plaintext
Raw Permalink Blame History

This file contains invisible Unicode characters

This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

The Linux keyboard and console HOWTO
Andries Brouwer, aeb@cwi.nl
v2.13, 2002-10-12
This note contains some information about the Linux keyboard and con­
sole, and the use of non-ASCII characters. It describes Linux 2.0.
______________________________________________________________________
Table of Contents
1. Useful programs
2. Keyboard generalities
3. Console generalities
4. Resetting your terminal
4.1 Keyboard hardware reset
5. Delete and Backspace
5.1 How to tell Unix what character you want to use to delete the last typed character
5.1.1 `Getty used to do the right thing with DEL and BS but is broken now?'
5.1.2 `Login behaves differently at the first and second login attempts?'
5.2 How to tell Linux what code to generate when a key is pressed
5.2.1 `How do I get a dvorak keyboard?'
5.2.2 `Why doesn't the Backspace key generate BackSpace by default?'
5.3 How to tell X to interchange Delete and Backspace
5.4 How to tell emacs what to do when it receives a Delete or Backspace
5.5 How to tell emacs to interchange Delete and Backspace
5.6 How to tell kermit to interchange Delete and Backspace
5.7 How to tell xterm to interchange Delete and Backspace
5.8 How to tell xterm about your favourite tty modes
5.9 How to tell non-Motif X applications that the Del key deletes forward
5.10 How to tell xmosaic that the Backspace key generates a DEL
5.11 A better solution for Motif-using programs, like netscape
5.12 What about termcap and terminfo?
5.13 A complete solution
6. The console character sets
7. Console switching
7.1 Changing the number of Virtual Consoles
8. Ctrl-Alt-Del and other special key combinations
8.1 Ctrl-Alt-Del (Boot)
8.2 Other combinations
8.3 X Combinations
8.4 Dosemu Combinations
8.5 Composing symbols
8.6 The SysRq key
8.7 Problems
9. How to get out of raw mode
10. The keyboard LEDs
11. The TERM variable
11.1 Terminfo
12. How to make other programs work with non-ASCII chars
13. X
13.1 What precisely does XFree86-2.1 do when it initializes its keymap?
14. Unusual keys and keyboards
14.1 Funkeys
15. Examples of use of loadkeys and xmodmap
15.1 `I can use only one finger to type with'
15.2 Sticky keys under
16. Changing the video mode
16.1 Instructions for the use of resizecons
17. Changing the keyboard repeat rate
18. Scrolling
19. Screensaving
20. Screen dumps
21. Some properties of the VT100 - application key mode
22. Hardware incompatibility
23. Copyright
______________________________________________________________________
1. Useful programs
The following packages contain keyboard or console related programs.
kbd-1.06.tar.gz contains loadkeys, dumpkeys, showkey, setmetamode,
setleds, setfont, showconsolefont, mapscrn, kbd_mode, kbdrate,
loadunimap, chvt, resizecons, deallocvt, getkeycodes, setkeycodes. It
also contains openvt, formerly called open.
There exists a clone of the kbd package, namely console-tools, that
contains more or less the same stuff. The latest version, console-
tools-0.3.3 is roughly up-to-date with kbd-0.99.
SVGATextMode-1.10 contains SVGATextMode, a program that obsoletes
resizecons.
util-linux-2.11 contains setterm.
sh-utils-1.12 contains stty.
See also dynamic-vc-1.2.tar.gz and consd-1.3.tgz for programs that
exploit the `Keyboard Signal' key. Very primitive versions are
spawn_login or spawn_console found in the kbd package.
See font.tgz for a package that handles console fonts.
Packages like recode and konwert-1.8 allow one to convert between
different character encodings.
The X distribution contains xmodmap, xset, kbd_mode. (See also
X386keybd(1) for the situation under XFree86 1.3, and Xserver(1) for
the XKEYBOARD extension under X11R6.) A handy interface to xmodmap is
xkeycaps, see http://www.jwz.org/xkeycaps/.
termcap-2.0.8.tar.gz contains termcap, an old terminal capabilities
data base. ncurses-1.9.9e.tar.gz contains the termlib data base which
obsoletes termcap. (However, there are still many programs using
termcap.)
See loadkeys(1), setleds(1) and setmetamode(1) for the codes generated
by the various keys and the setting of leds when not under X. Under X,
see xmodmap(1) and xset(1).
See setfont(8) for loading console fonts. Many people will want to
load a font like iso01.f16 because the default font is the hardware
font of the video card, and often is a `Code Page 437' font missing
accented characters and other Latin-1 symbols.
See setterm(1) and kbdrate(8) for properties such as foreground and
background colors, screen blanking and character repeat rate when not
under X. Under X, see xset(1), also for key click and bell volume.
The file /etc/termcap defines the escape sequences used by many
programs addressing the console (or any other terminal). See
termcap(5). A more modern version is found in /usr/lib/terminfo. See
terminfo(5). Terminfo files are compiled by the terminfo compiler
/usr/lib/terminfo/tic, see tic(1). Their contents can be examined
using the program infocmp, see infocmp(1).
The Linux console sequences are documented in console_codes(4).
The package funkey by Rick van Rein provides support for all these new
keys modern keyboards have. See rick.vanrein.org/linux/funkey.
2. Keyboard generalities
You press a key, and the keyboard controller sends scancodes to the
kernel keyboard driver. Some keyboards can be programmed, but usually
the scancodes corresponding to your keys are fixed. The kernel
keyboard driver just transmits whatever it receives to the application
program when it is in scancode mode, like when X is running.
Otherwise, it parses the stream of scancodes into keycodes,
corresponding to key press or key release events. (A single key press
can generate up to 6 scancodes.) These keycodes are transmitted to
the application program when it is in keycode mode (as used, for
example, by showkey and some X servers). Otherwise, these keycodes
are looked up in the keymap, and the character or string found there
is transmitted to the application, or the action described there is
performed. (For example, if one presses and releases the a key, then
the keyboard produces scancodes 0x1e and 0x9e, this is converted to
keycodes 30 and 158, and then transmitted as 0141, the ASCII or
latin-1 code for `a'; if one presses and releases Delete, then the
keyboard produces scancodes 0xe0 0x53 0xe0 0xd3, these are converted
to keycodes 111 and 239, and then transmitted as the 4-symbol sequence
ESC [ 3 ~, all assuming a US keyboard and a default keymap. An example
of a key combination to which an action is assigned is Ctrl-Alt-Del.)
The translation between unusual scancodes and keycodes can be set
using the utility setkeycodes - only few people will need it. The
translation between keycodes and characters or strings or actions,
that is, the keymap, is set using the utilities loadkeys and
setmetamode. For details, see getkeycodes(8), setkeycodes(8),
dumpkeys(1), loadkeys(1), setmetamode(1). The format of the files
output by dumpkeys and read by loadkeys is described in keymaps(5).
Where it says `transmitted to the application' in the above
description, this really means `transmitted to the terminal driver'.
That is, further processing is just like that of text that comes in
over a serial line. The details of this processing are set by the
program stty.
3. Console generalities
Conversely, when you output something to the console, it first
undergoes the standard tty processing, and then is fed to the console
driver. The console driver emulates a VT100, and parses the input in
order to recognize VT100 escape sequences (for cursor movement, clear
screen, etc.). The characters that are not part of an escape sequence
are first converted into Unicode, using one of four mapping tables if
the console was not in UTF-8 mode to start with, then looked up in the
table describing the correspondence between Unicode values and font
positions, and the obtained 8- or 9-bit font indices are then written
to video memory, where they cause the display of character shapes
found in the video card's character ROM. One can load one's own fonts
into character ROM using setfont. The obsolete programs loadunimap
and mapscrn can be used to manipulate the Unicode map belonging to the
font, or the mapping table of the console. More details will be given
below.
There are many consoles (called Virtual Consoles or Virtual Terminals,
abbreviated VCs or VTs) that share the same screen. You can use them
as independent devices, either to run indendent login sessions, or
just to send some output to, perhaps from top, or the tail of the
system log or so. See below (`Console switching') on how to set them
up and switch between them.
4. Resetting your terminal
There is garbage on the screen, or all your keystrokes are echoed as
line drawing characters. What to do?
Many programs will redraw the screen when Ctrl-L is typed. This might
help when there is some modem noise or broadcast message on your
screen. The command clear will clear the screen.
The command reset will reset the console driver. This helps when the
screen is full of funny graphic characters, and also if it is reduced
to the bottom line. If you don't have this command, or if it does
something else, make your own by putting the following two lines in an
executable file reset in your PATH:
#!/bin/sh
echo -e \\033c
that is, you want to send the two characters ESC c to the console.
Why is it that the display sometimes gets confused and gives you a
24-line or 1-line screen, instead of the usual 25 lines? Well, the
main culprit is the use of TERM=vt100 (or some other entry with 24
lines) instead of TERM=linux when logged in remotely. If this happens
on /dev/tty2 then typing
% cat > /dev/tty2
^[c
^D
on some other VT (where 4 symbols are typed to cat: ESC, c, ENTER,
Ctrl-D) and refreshing the screen on /dev/tty2 (perhaps using Ctrl-L)
will fix things. Of course the permanent fix is to use the right term­
cap or terminfo entry. A command that only changes the number of
lines is
% echo -e "\033[1;25r"
Why is it that you sometimes get a lot of line-drawing characters,
e.g., after catting a binary to the screen? Well, there are various
character set changing escape sequences, and by accident your binary
might contain some of these. The ESC c is a general reset, a cure for
all, but if you know precisely what went wrong you can repair it
without resetting other console attributes. For example, after
% cat
^N
^D
your shell prompt will be all line-drawing characters. Now do (typing
blindly)
% cat
^O
^D
and all is well again. (Three symbols typed to each cat: Ctrl-N (or
Ctrl-O), ENTER, Ctrl-D.) To understand what is happening, see `The
console character sets' below.
If you loaded some strange font, and want to return to the default,
% setfont
will do (provided you stored the default font in the default place).
If this default font does not contain an embedded Unicode map (and
gives the wrong symbols for accented characters), then say
% loadunimap
For example, if I do
% loadkeys de-latin1
then I have a German keyboard, and the key left of the Enter key gives
me a-umlaut. This works, because the a-umlaut occurs on the CP437 code
page and the kernel Unicode map is initialized to CP437, and my video
card has a CP437 font built-in. If I now load an ISO 8859-1 font with
% setfont iso01.f16
then everything still works, because setfont invalidates the kernel
Unicode map (if there is no Unicode map attached to the font), and
without map the kernel goes directly to the font, and that is pre­
cisely correct for an ISO 8859-1 system with iso01.f16 font. But
going back to the previous font with
% setfont
gives capital Sigma's instead of a-umlaut - all accented letters are
mixed up because also this font has no embedded Unicode map. After
% loadunimap
which loads the default Unicode map (which is right for the default
font) all works correctly again. Usually loadunimap is not invoked
directly, but via setfont. Thus, the previous two commands may be
replaced by
% setfont -u def
These days most fonts have embedded Unicode maps (often this is indi­
cated by the extension .psfu), and none of this nonsense is needed
anymore.
On very old terminals output involving tabs may require a delay, and
you have to say
% stty tab3
(see stty(1)).
You can change the video mode using resizecons or SVGATextMode. Or by
rebooting and having "vga=ask" in the LILO configuration file.
This usually settles the output side.
On the input side there are many things that might be wrong. If X or
DOOM or some other program using raw mode crashed, your keyboard may
still be in raw (or mediumraw) mode, and it is difficult to give
commands. (See "How to get out of raw mode" below.) If you loaded a
bad keymap, then
% loadkeys -d
loads the default map again, but it may well be difficult to type `-'!
An alternative is
% loadkeys defkeymap
Sometimes even the letters are garbled. It is useful to know that
there are four main types of keyboards: QWERTY, QWERTZ, AZERTY and
DVORAK. The first three are named after the first six letter keys,
and roughly represent the English, German and French speaking coun­
tries. Compared to QWERTY, the QWERTZ map interchanges Y and Z. Com­
pared to QWERTY, the AZERTY map interchanges Q and A, W and Z, and has
its M right of the L, at the semicolon position. DVORAK has an
entirely different letter ordering. There are two types of Turkish
keyboard. The so-called `Q'-keyboard has a QWERTY layout, while the
`F'-keyboard has an entirely different layout, let us say fgGIod,
where G stands for Gbreve and I for dotlessi.
4.1. Keyboard hardware reset
Things may be wrong on a lower level than Linux knows about. There
are at least two distinct lower levels (keyboard and keyboard
controller) where one can give the command "keyboard disable" to the
keyboard hardware. Keyboards can often be programmed to use one out
of three different sets of scancodes.
However, I do not know of cases where this turned out to be a problem.
Some keyboards have a remapping capability built in. Stormy Henderson
(stormy@Ghost.Net) writes: `If it's your keyboard accidently being
reprogrammed, you can (on a Gateway AnyKey keyboard) press control-
alt-suspend_macro to reset the keys to normal.'
5. Delete and Backspace
Getting Delete and Backspace to work just right is nontrivial,
especially in a mixed environment, where you talk to console, to X, to
bash, to emacs, login remotely, etc. You may have to edit several
configuration files to tell all of the programs involved precisely
what you want. On the one hand, there is the matter of which keys
generate which codes (and how these codes are remapped by e.g. kermit
or emacs), and on the other hand the question of what functions are
bound to what codes.
People often complain `my backspace key does not work', as if this key
had a built-in function `delete previous character'. Unfortunately,
all this key, or any key, does is producing a code, and one only can
hope that the kernel tty driver and all application programs can be
configured such that the backspace key indeed does function as a
`delete previous character' key.
Most Unix programs get their tty input via the kernel tty driver in
`cooked' mode, and a simple stty command determines the erase
character. However, programs like bash and emacs and X do their own
input handling, and have to be convinced one-by-one to do the right
thing.
5.1. How to tell Unix what character you want to use to delete the
last typed character
% stty erase ^?
If the character is erased, but in a funny way, then something is
wrong with your tty settings. If echoprt is set, then erased charac­
ters are enclosed between \ and /. If echoe is not set, then the
erase char is echoed (which is reasonable when it is a printing char­
acter, like #). Most people will want stty echoe -echoprt. Saying
stty sane will do this and more. Saying stty -a shows your current
settings. How come this is not right by default? It is, if you use
the right getty.
Note that many programs (like bash, emacs etc.) have their own
keybindings (defined in ~/.inputrc, ~/.emacs etc.) and are unaffected
by the setting of the erase character.
The standard Unix tty driver does not recognize a cursor, or keys
(like the arrow keys) to move the current position, and hence does not
have a command `delete current character' either. But for example you
can get bash on the console to recognize the Delete key by putting
set editing-mode emacs
"\e[3~":delete-char
into ~/.inputrc.
5.1.1. `Getty used to do the right thing with DEL and BS but is bro­
ken now?'
Earlier, the console driver would do BS Space BS (\010\040\010) when
it got a DEL (\177). Nowadays, DEL's are ignored (as they should be,
since the driver emulates a vt100). Get a better getty, i.e., one that
does not output DEL.
5.1.2. `Login behaves differently at the first and second login
attempts?'
At the first attempt, you are talking to getty. At the second attempt,
you are talking to login, a different program.
5.2. How to tell Linux what code to generate when a key is pressed
On the console, or, more precisely, when not in (MEDIUM)RAW mode, use
% loadkeys mykeys.map
and under X use
% xmodmap mykeys.xmap
Note that (since XFree86-2.1) X reads the Linux settings of the
keymaps when initialising the X keymap. Although the two systems are
not 100% compatible, this should mean that in many cases the use of
xmodmap has become superfluous.
For example, suppose that you would like the Backspace key to send a
BackSpace (Ctrl-H, octal 010) and the grey Delete key a DEL (octal
0177). Add the following to /etc/rc.local (or wherever you keep your
local boot-time stuff):
/usr/bin/loadkeys << EOF
keycode 14 = BackSpace
keycode 111 = Delete
EOF
Note that this will only change the function of these keys when no
modifiers are used. (You need to specify a keymaps line to tell which
keymaps should be affected if you want to change bindings on more
keymaps.) The Linux kernel default lets Ctrl-Backspace generate
BackSpace - this is sometimes useful as emergency escape, when you
find you can only generate DELs.
The left Alt key is sometimes called the Meta key, and by default the
combinations AltL-X are bound to the symbol MetaX. But what character
sequence is MetaX? That is determined (per-tty) by the Meta flag, set
by the command setmetamode. The two choices are: ESC X or X or-ed with
0200.
Many distributions have a loadkeys command somewhere in the bootup
sequence. For example, one may have the name of the desired keymap in
/etc/sysconfig/keyboard and the loadkeys command that loads it in
/etc/rc.d/init.d/keytable. Or one may have the actual default keymap
in /etc/default.keytab and the loadkeys command that loads it in
/etc/rc.d/boot. Etc. Instead of adding a local modification to the
default, one can of course change the default by editing the default
keymap or changing the name of the keymap to be loaded at boot time.
Note that loadkeys itself has default keymap defkeymap.map located
somewhere under /usr/lib/kbd or /usr/share/kbd (just like all other
keymaps) and this may not yet be available in single user boot before
/usr has been mounted.
5.2.1. `How do I get a dvorak keyboard?'
The command
% loadkeys dvorak
will give you a dvorak layout, probably by loading something like
/usr/lib/kbd/keymaps/i386/dvorak/dvorak.map.gz. Under X, put
XkbLayout "dvorak"
in XF86Config.
5.2.2. `Why doesn't the Backspace key generate BackSpace by default?'
(i) Because the VT100 had a Delete key above the Enter key.
(ii) Because Linus decided so.
5.3. How to tell X to interchange Delete and Backspace
% xmodmap -e "keysym BackSpace = Delete" -e "keysym Delete = BackSpace"
Or, if you just want the Backspace key to generate a BackSpace:
% xmodmap -e "keycode 22 = BackSpace"
Or, if you just want the Delete key to generate a Delete:
% xmodmap -e "keycode 107 = Delete"
(but usually this is the default binding already).
5.4. How to tell emacs what to do when it receives a Delete or
Backspace
Put in your .emacs file lines like
(global-set-key "\?" 'help-command)
(global-set-key "\C-h" 'delete-backward-char)
Of course you can bind other commands to other keys in the same way.
Note that various major and minor modes redefine keybindings. For
example, in incremental search mode one finds the code
(define-key map "\177" 'isearch-delete-char)
(define-key map "\C-h" 'isearch-mode-help)
This means that it may be a bad idea to use the above two global-set-
key commands. There are too many places where there are built-in
assumptions about Ctrl-H = help and DEL = delete. That doesn't mean
that you have to setup keys so that Backspace generates DEL. But if it
doesn't then it is easiest to remap them at the lowest possible level
in emacs.
5.5. How to tell emacs to interchange Delete and Backspace
Put in your .emacs file lines
(setq keyboard-translate-table (make-string 128 0))
(let ((i 0))
(while (< i 128)
(aset keyboard-translate-table i i)
(setq i (1+ i))))
(aset keyboard-translate-table ?\b ?\^?)
(aset keyboard-translate-table ?\^? ?\b)
Recent versions of emacs have a function keyboard-translate and one
may simplify the above to
(keyboard-translate ?\C-h ?\C-?)
(keyboard-translate ?\C-? ?\C-h)
Note that under X emacs can distinguish between Ctrl-h and the
Backspace key (regardless of what codes these produce on the console),
and by default emacs will view the Backspace key as DEL (and do dele­
tion things, as bound to that character, rather than help things,
bound to Ctrl-H). One can distinguish Backspace and Delete, e.g. by
(global-unset-key [backspace] )
(global-set-key [backspace] 'delete-backward-char)
(global-unset-key [delete] )
(global-set-key [delete] 'delete-char)
5.6. How to tell kermit to interchange Delete and Backspace
Put in your .kermrc file the lines
set key \127 \8
set key \8 \127
5.7. How to tell xterm to interchange Delete and Backspace
XTerm*VT100.Translations: #override\n\
<KeyPress> BackSpace : string(0x7f)\n\
<KeyPress> Delete : string(0x08)\n
5.8. How to tell xterm about your favourite tty modes
Normally xterm will inherit the tty modes from its invoker. Under
xdm, the default erase and kill characters are # and @, as in good old
Unix Version 6. If you don't like that, you might put something like
XTerm*ttymodes: erase ^? kill ^U intr ^C quit ^\ eof ^D \
susp ^Z start ^Q stop ^S eol ^@
in /usr/lib/X11/app-defaults/XTerm or in $HOME/.Xresources, assuming
that you have a line
xrdb -merge $HOME/.Xresources
in your $HOME/.xinitrc or $HOME/.xsession.
5.9. How to tell non-Motif X applications that the Del key deletes
forward
Put
*Text.translations: #override \
~Shift ~Meta <Key>Delete: delete-next-character()
into .Xresources to make non-Motif X applications such as xfig, xedit,
etc., work correctly. (Daniel T. Cobra)
5.10. How to tell xmosaic that the Backspace key generates a DEL
Putting
*XmText.translations: #override\n\
<Key>osfDelete: delete-previous-character()
*XmTextField.translations: #override\n\
<Key>osfDelete: delete-previous-character()
in your $HOME/.Xdefaults or $HOME/.Xresources helps. (What file? The
file that is fed to xrdb, for example in .xinitrc.)
The netscape FAQ, however, says:
Why doesn't my Backspace key work in text fields?
By default, Linux and XFree86 come with the Backspace and Delete keys
misconfigured. All Motif programs (including, of course, Netscape
Navigator) will malfunction in the same way.
The Motif spec says that Backspace is supposed to delete the previous
character and Delete is supposed to delete the following character.
Linux and XFree86 come configured with both the Backspace and Delete
keys generating Delete.
You can fix this by using any one of the xmodmap, xkeycaps, or
loadkeys programs to make the key in question generate the BackSpace
keysym instead of Delete.
You can also fix it by having a .motifbind file; see the man page
for VirtualBindings(3).
Note: Don't use the *XmText.translations or *XmTextField.translations
resources to attempt to fix this problem. If you do, you will blow
away Netscape Navigator's other text-field key bindings.
5.11. A better solution for Motif-using programs, like netscape
Ted Kandell (ted@tcg.net) suggests the following:
Somewhere in your .profile add the following:
stty erase ^H
If you are using bash, add the following lines to your .inputrc:
"\C-?": delete-char
"\C-h": backward-delete-char
Add the following lines to your .xinitrc file:
xmodmap <<-EOF
keycode 22 = BackSpace osfBackSpace
keycode 107 = Delete
EOF
# start your window manager here, for example:
#(fvwm) 2>&1 | tee /dev/tty /dev/console
stty sane
stty erase ^H
loadmap <<-EOF
keycode 14 = BackSpace
keycode 111 = Delete
EOF
This will definitely work for a PC 101 or 102 key keyboard with any
Linux/XFree86 layout.
The important part to making Motif apps like Netscape work properly is
adding osfBackSpace to keycode 22 in addition to BackSpace.
Note that there must be spaces on either side of the = sign.
5.12. What about termcap and terminfo?
When people have problems with backspace, they tend to look at their
termcap (or terminfo) entry for the terminal, and indeed, there does
exist a kb (or kbs) capability describing the code generated by the
Backspace key. However, not many programs use it, so unless you are
having problems with one particular program only, probably the fault
is elsewhere. Of course it is a good idea anyway to correct your
termcap (terminfo) entry. See also below under "The TERM variable".
5.13. A complete solution
There are many possibilities to get a functioning system. Can't you
give one complete set of settings that works?
One way of getting a setup that works in all contexts is to have the
Backspace key generate DEL when on the console (or xterm), and
BackSpace when under X. Maybe that is most convenient - there are too
many X utilities that expect BackSpace, and emacs on the console or
xterm expects DEL, while emacs under X can distinguish [BackSpace]
from Ctrl-H and does the right thing.
What is needed? No loadkeys changes, since the Backspace key already
generates DEL by default. No stty settings, they are OK by default.
No X settings, they are OK by default. One just has to tell xterm
that the Backspace key should generate DEL: put
XTerm*VT100.Translations: #override\n\
<KeyPress> BackSpace : string(0x7f)\n\
in .Xresources, and
xrdb -merge .Xresources
in .xinitrc, and you are settled.
For a much more extensive discussion of these things, and alternative
solutions, see Anne Baretta's page.
6. The console character sets
The kernel first tries to figure out what symbol is meant by any given
user byte, and next where this symbol is located in the current font.
The kernel knows about 5 translations of bytes into console-screen
symbols. In Unicode (UTF-8) mode, the UTF-8 code is just converted
directly into Unicode. The assumption is that almost all symbols one
needs are present in Unicode, and for the cases where this does not
hold the codes 0xf000-0xf1ff are reserved for direct font access.
When not in Unicode mode, one of four translation tables is used. The
four tables are: a) Latin1 -> Unicode, b) VT100 graphics -> Unicode,
c) PC -> Unicode, d) user-defined.
There are two character sets, called G0 and G1, and one of them is the
current character set. (Initially G0.) Typing Ctrl-N causes G1 to
become current, Ctrl-O causes G0 to become current.
These variables G0 and G1 point at a translation table, and can be
changed by the user. Initially they point at tables a) and b),
respectively. The sequences ESC ( B and ESC ( 0 and ESC ( U and ESC (
K cause G0 to point at translation table a), b), c) and d),
respectively. The sequences ESC ) B and ESC ) 0 and ESC ) U and ESC )
K cause G1 to point at translation table a), b), c) and d),
respectively.
The sequence ESC c causes a terminal reset, which is what you want if
the screen is all garbled. The oft-advised echo ^V^O will only make G0
current, but there is no guarantee that G0 points at table a). In
some distributions there is a program reset(1) that just does echo
^[c. If your termcap entry for the console is correct (and has an
entry :rs=\Ec:), then also setterm -reset will work.
The user-defined mapping table can be set using mapscrn(8). The
result of the mapping is that if a symbol c is printed, the symbol s =
map[c] is sent to the video memory. The bitmap that corresponds to s
is found in the character ROM, and can be changed using setfont(8).
7. Console switching
By default, console switching is done using Alt-Fn or Ctrl-Alt-Fn.
Under X (or recent versions of dosemu), only Ctrl-Alt-Fn works. Many
keymaps will allow cyclic walks through all allocated consoles using
Alt-RightArrow and Alt-LeftArrow.
XFree86 1.3 does not know that Alt is down when you switch to the X
window. Thus, you cannot switch immediately to some other VT again but
have to release Alt first. In the other direction this should work:
the kernel always keeps track of the up/down status of all keys. (As
far as possible: on some keyboards some keys do not emit a scancode
when pressed (e.g.: the PFn keys of a FOCUS 9000) or released (e.g.:
the Pause key of many keyboards).)
XFree86 1.3 saves the fonts loaded in the character ROMs when started,
and restores it on a console switch. Thus, the result of setfont on a
VT is wiped out when you go to X and back. Using setfont under X will
lead to funny results.
One can change VT under program control using the chvt command.
7.1. Changing the number of Virtual Consoles
This question still comes up from time to time, but the answer is: you
already have enough of them. Since kernel version 1.1.54, there are
between 1 and 63 virtual consoles. A new one is created as soon as it
is opened. It is removed by the utility deallocvt (but it can be
removed only when no processes are associated to it anymore, and no
text on it has been selected by programs like selection or gpm).
For older kernels, change the line
#define NR_CONSOLES 8
in include/linux/tty.h (don't increase this number beyond 63), and
recompile the kernel.
If they do not exist yet, create the tty devices with MAKEDEV or mknod
ttyN c 4 N where N denotes the tty number. For example,
for i in 9 10 11 12; do mknod /dev/tty$i c 4 $i; done
or, better (since it also takes care of owner and permissions),
for i in 9 10 11 12; do /dev/MAKEDEV tty$i; done
If you want the new VCs to run getty, add lines in /etc/inittab. (But
it is much better to have only two getty's running, and to create more
consoles dynamically as the need arises. That way you'll have more
memory when you don't use all these consoles, and also more consoles,
in case you really need them. Edit /etc/inittab and comment out all
getty's except for the first two.)
When the consoles are allocated dynamically, it is usually easiest to
have only one or two running getty. More are opened by open -l -s
bash. Unused consoles (without associated processes) are deallocated
using deallocvt (formerly disalloc). But, you say, I am involved in
activities when I suddenly need more consoles, and do not have a bash
prompt available to give the open command. Fortunately it is possible
to create a new console upon a single keystroke, regardless of what is
happening at the current console.
If you have spawn_login from kbd-1.04.tar.gz and you put
loadkeys << EOF
alt keycode 103 = Spawn_Console
EOF
spawn_login &
in /etc/rc.local, then typing Alt-UpArrow will create a fresh VC run­
ning login (and switch to it). With spawn_console & instead of
spawn_login & you'll have bash running there. See also open-1.4.tgz
and dynamic-vc-1.1.tar.gz.
What action should be taken upon this Spawn_Console keypress can also
be set in /etc/inittab under kbrequest, if you have a recent init. See
inittab(5).
(This action can be something entirely different - I just called the
key Spawn_Console because that is what I used it for. When used for
other purposes it is less confusing to use its synonym KeyboardSignal.
For example, some people like to put the lines
kb::kbrequest:/sbin/shutdown -h now
in /etc/inittab, and
control alt keycode 79 = KeyboardSignal
control alt keycode 107 = KeyboardSignal
in their keymap. Now Ctrl-Alt-End will do a system shutdown.)
You can only login as "root" on terminals listed in /etc/securetty.
There exist programs that read terminal settings from files /etc/ttys
and /etc/ttytype. If you have such files, and create additional
consoles, then it might be a good idea to also add entries for them in
these files.
8. Ctrl-Alt-Del and other special key combinations
8.1. Ctrl-Alt-Del (Boot)
If you press Ctrl-Alt-Del (or whatever key was assigned the keysym
Boot by loadkeys) then either the machine reboots immediately (without
sync), or init is sent a SIGINT. The former behaviour is the default.
The default can be changed by root, using the system call reboot(),
see ctrlaltdel(8). Some init's change the default. What happens when
init gets SIGINT depends on the version of init used - often it will
be determined by the pf entry in /etc/inittab (which means that you
can run an arbitrary program in this case). In the current kernel
Ctrl-AltGr-Del is no longer by default assigned to Boot.
8.2. Other combinations
Name Default binding
-------------------------------
Show_Memory Shift-Scrollock
Show_Registers AltGr-ScrollLock
Show_State Ctrl-ScrollLock
Console_n Alt-Fn and Ctrl-Alt-Fn (1 <= n <= 12)
Console_{n+12} AltGr-Fn (1 <= n <= 12)
Incr_Console Alt-RightArrow
Decr_Console Alt-LeftArrow
Last_Console Alt[Gr]-PrintScreen
Scroll_Backward Shift-PageUp
Scroll_Forward Shift-PageDown
Caps_On (CapsLock is a toggle; this key sets)
Compose Ctrl-.
8.3. X Combinations
Ctrl-Alt-Fn Switch to VT n
Ctrl-Alt-KP+ Next mode
Ctrl-Alt-KP- Previous mode
Ctrl-Alt-Backspace Kill X
On some motherboards, Ctrl-Alt-KP- and Ctrl-Alt-KP+ will be equivalent
to pressing the Turbo button. That is, both will produce the scancodes
1d 38 4a ca b8 9d and 1d 38 4e ce b8 9d, and both will switch between
Turbo (>= 25MHz) and non-Turbo (8 or 12 MHz). (Often these key combi­
nations only function this way when enabled by jumpers on the mother­
board.)
Perry F Nguyen (pfnguyen@netcom22.netcom.com) writes: AMI BIOS has a
feature that locks up the keyboard and flashes the LED's if the Ctrl-
Alt-Backspace combination is pressed while a BIOS password is enabled,
until the CMOS/BIOS password is typed in.
On some SiS based motherboards the combination Ctrl-Alt-Backspace will
cause a power off, or puts the machine in power save mode. (Reported
for SiS 630 and for SiS645DX.)
8.4. Dosemu Combinations
Ctrl-Alt-Fn Switch to VT n (from version 0.50; earlier Alt-Fn)
Ctrl-Alt-PgDn Kill dosemu (when in RAW keyboard mode)
(and many other combinations - see the dosemu documentation)
8.5. Composing symbols
One symbol may be constructed using several keystrokes.
· LeftAlt-press, followed by a decimal number typed on the keypad,
followed by LeftAlt-release, yields the symbol with code given by
this number. (In Unicode mode this same mechanism, but then with 4
hexadecimal digits, may be used to define a Unicode symbol.)
· A dead diacritic followed by a symbol, yields that symbol adorned
with that diacritic. If the combination is undefined, both keys are
taken separately. Which keys are dead diacritics is user-settable;
none is by default. Five (since 2.0.25 six) dead diacritics can be
defined (using loadkeys(1)): dead_grave, dead_acute,
dead_circumflex, dead_tilde, dead_diaeresis (and dead_cedilla).
Precisely what this adorning means is also user-settable: dead-
diacritic, symbol is equivalent to Compose + diacritic + symbol.
· Compose followed by two symbols yields a combination symbol. These
combinations are user-settable. Today there are 68 combinations
defined by default; you can see them by saying "dumpkeys | grep
compose".
· Then there are `Sticky' modifier keys (since 1.3.33). For example,
one can type Ctrl-C as SControl, C and Ctrl-Alt-BackSpace as
SControl, SAlt, BackSpace.
Note that there are at least four such composition mechanisms:
1. The Linux keyboard driver mechanism, used in conjunction with
loadkeys.
2. The X mechanism - see X386keybd(1), later XFree86kbd(1). Under
X11R6: edit /usr/X11R6/lib/X11/locale/iso8859-1/Compose.
See also Andrew D. Balsa's comments at
http://wauug.erols.com/~balsa/linux/deadkeys/index.html.
3. The emacs mechanism obtained by loading "iso-insert.el" or calling
`iso-accents-mode'.
4. The vim mechanism: insert a composed symbol by pressing Ctrl-K
followed by two symbols. A list of the possible combinations is
obtained by the command :digraphs.
For X the order of the two symbols is arbitrary: both Compose-,-c
and Compose-c-, yield a c-cedilla; for Linux and emacs only the
former sequence works by default. For X and vim the list of compose
combinations is fixed. Linux and emacs are flexible. The default
lists are somewhat similar, but the details are different.
8.6. The SysRq key
In case your kernel was compiled with CONFIG_MAGIC_SYSRQ enabled (a
feature that is present since Linux 2.1.43) there is a single key
(defined in <linux/keyboard.h>) to which special system functions are
attached, regardless of the current keyboard mode. For the PC
architecture this special key is, naturally, the Alt+SysRq key, and
any of the two Alt keys will work. (Note that if CONFIG_MAGIC_SYSRQ
was not enabled, the default action of this key is to return to the
previous console.)
If you press this key, do not release it, and hit another key, a
corresponding action is performed. The action is performed whether
anybody is logged in or not, is root or not. For the details, see
drivers/char/sysrq.c. Since this feature is meant only for kernel
hackers, that should suffice. Still, let me add a few remarks.
For the key r the keyboard mode is reset to K_XLATE. For the key k a
SAK and console reset is done. For the key b the machine is rebooted
immediately. (See, not something you want to have enabled on a
production machine.) For the key o the power is turned off (when the
machine is capable of that). For the key s an emergency sync is
scheduled. For the key u an emergency read-only remount is scheduled.
For the keys p,t,m various information is shown (namely the same
information also shown for RAlt,RCtrl,RShift+ScrollLock). For the
keys e,i,l all processes get a SIG_TERM or SIG_KILL, respectively; for
l even the init process is killed. Digits set the log level. Anything
else prints a short summary: SysRq: unRaw saK Boot Off Sync Unmount
showPc showTasks showMem loglevel0-8 tErm kIll killalL.
Note: These are very dangerous actions! And they do not use your
keymap - indeed, are meant for emergency cases where the state of your
keymap, or even of the entire kernel, is uncertain. If you use a
dvorak keyboard - bad luck! Most other people will be able to survive:
the dangerous letters A,M,Q,W,Y,Z that are differently placed on
English, French and German keyboards, are not used for actions. (But
if your finger slips and you hit L instead of K - bye bye to your
system.)
In Linux 2.3.13 the possibility to enable/disable SysRq was added.
echo 0 > /proc/sys/kernel/sysrq
will disable it (if the kernel was compiled with CONFIG_MAGIC_SYSRQ).
8.7. Problems
A good keyboard accurately reports multiple key presses. Especially
for people using a keyboard as Braille input device, where they have
to be able to press up to six keys simultaneously, this is important.
Many modern keyboards fail here due to sloppy design and testing -
they misreport or fail in other ways when four or more keys are
pressed simultaneously, sometimes already when two non-modifier keys
are pressed simultaneously. This affects Linux users a bit: the SysRq
key is not a modifier key, and people report problems using Alt-SysRq-
X for various letters or digits X.
Long ago a similar problem (`ghosting') was caused by the design of
the scan matrix: when three keys were pressed a fourth was also seen.
That problem was solved by the use of diodes. Today it is the
interface logic that is deficient.
9. How to get out of raw mode
If some program using K_RAW keyboard mode exits without restoring the
keyboard mode to K_XLATE, then it is difficult to do anything - not
even Ctrl-Alt-Del works. However, it is sometimes possible to avoid
hitting the reset button. (And desirable as well: your users may get
angry if you kill their Hack game by rebooting; you might also damage
your file system.) Easy solutions involve logging in from another
terminal or another machine and doing kbd_mode -a. The procedure
below assumes that no X is running, that the display is in text mode,
and that you are at your bash prompt, that you are using a US keyboard
layout, and that your interrupt character is Ctrl-C.
Step 1. Start X. As follows: press 2 (and don't release), press F12
(and don't release) and immediately afterwards press = . This starts
X. (Explanation: if a key press produces keycode K, then the key
release produces keycode K+128. Probably your shell does not like
these high characters, so we avoid generating them by not releasing
any key. However, we have to be quick, otherwise key repeat starts.
The digit 2 produces a Ctrl-C that discards previous junk, the F12
produces an X and the = a Return.) Probably your screen will be grey
now, since no .xinitrc was specified. However, Ctrl-Alt-Fn will work
and you can go to another VT. (Ctrl-Alt-Backspace also works, but
that exits X, and gets you back into the previous state, which is not
what you want.)
Step 2. Setup to change the keyboard mode. (For example, by sleep 5;
kbd_mode -a.)
Step 3. Leave X again. Alt-Fx (often Alt-F7) brings you back to X,
and then Ctrl-Alt-Backspace exits X. Within 5 seconds your keyboard
will be usable again.
If you want to prepare for the occasion, then make \215A\301 (3
symbols) an alias for kbd_mode -a. Now just hitting = F7 = (3
symbols) will return you to sanity.
10. The keyboard LEDs
1. There are per-tty keyboard flags: each VC has its own NumLock,
CapsLock, ScrollLock. By default these keyboard flags are shown in
the LEDs. The usual way to change them is by pressing the
corresponding key. (Side remark: pressing the NumLock key when in
application key mode will not change the NumLock status, but produce
an escape sequence. If you want the NumLock key to always change the
Numlock status, bind it to Bare_Num_Lock.)
2. Next, there are per-tty default keyboard flags, to initialize the
keyboard flags when a reset occurs. Thus if you want NumLock on all
the time, that is possible. The usual way to change them is by
`setleds -D ...'.
3. There is the possibility that the leds do not reflect the keyboard
flags, but something else.
3A. This something else can be three bits somewhere in the kernel -
which can be used if you want to monitor some hardware or software
status bit(s). If you want this, edit the kernel source to call
register_leds() somewhere.
3B. This something else can also be whatever some user program wants
to show in the LEDs. Thus, people who like such things can make nice
patterns of lights. If you want this, use the KDSETLED ioctl.
This latter use is not per-tty, but the choice between former and
latter use is per-tty.
Summarizing: Each tty has a flag kbd->ledmode. If this has the value
LED_SHOW_FLAGS then the keyboard flags (NumLock etc.) of that tty are
shown. If this has the value LED_SHOW_MEM then three selected memory
addresses are shown. If this has the value LED_SHOW_IOCTL then the
leds show whatever value was last assigned to them using the KDSETLED
ioctl.
One may add that X uses ioctl's to set the LEDs, but fails to reset
its VT when it exits, so after using X there may be one VT that is not
in the default LED_SHOW_FLAGS state. This can be fixed by doing
`setleds -L' on that VT. See setleds(1).
11. The TERM variable
Many programs use the TERM variable and the database /etc/termcap or
/usr/lib/terminfo/* to decide which strings to send for clear screen,
move cursor, etc., and sometimes also to decide which string is sent
by the users backspace key, function keys etc. This value is first
set by the kernel (for the console). Usually, this variable is re-set
by getty, using /etc/ttytype or the argument specified in
/etc/inittab. Sometimes, it is also set in /etc/profile.
Older systems use TERM=console or TERM=con80x25. Newer systems (with
ncurses 1.8.6) use the more specific TERM=linux or TERM=linux-80x25.
However, old versions of setterm test for TERM=con* and hence fail to
work with TERM=linux.
Since kernel version 1.3.2, the kernel default for the console is
TERM=linux.
If you have a termcap without entry for linux, add the word linux to
the entry for the console:
console|con80x25|linux:\
and make /usr/lib/terminfo/l/linux a copy of or symbolic link to
/usr/lib/terminfo/c/console.
11.1. Terminfo
The terminfo entry for the linux console from ncurses 1.8.6 misses the
entry kich1=\E[2~, needed by some programs. Edit the file and tic it.
12. How to make other programs work with non-ASCII chars
In the bad old days this used to be quite a hassle. Every separate
program had to be convinced individually to leave your bits alone.
Not that all is easy now, but recently a lot of gnu utilities have
learned to react to LC_CTYPE=iso_8859_1 or LC_CTYPE=iso-8859-1. Try
this first, and if it doesn't help look at the hints below. Note that
in recent versions of libc the routine setlocale() only works if you
have installed the locale files (e.g. in /usr/lib/locale).
First of all, the 8-th bit should survive the kernel input processing,
so make sure to have stty cs8 -istrip -parenb set.
A. For emacs the details strongly depend on the version. The
information below is for version 19.34. Put lines
(set-input-mode nil nil 1)
(standard-display-european t)
(require 'iso-syntax)
into your $HOME/.emacs. The first line (to be precise: the final 1)
tells emacs not to discard the 8-th bit from input characters. The
second line tells emacs not to display non-ASCII characters as octal
escapes. The third line specifies the syntactic properties and case
conversion table for the Latin-1 character set These last two lines
are superfluous if you have something like LC_CTYPE=ISO-8859-1 in your
environment. (The variable may also be LC_ALL or even LANG. The
value may be anything with a substring `88591' or `8859-1' or
`8859_1'.)
This is a good start. On a terminal that cannot display non-ASCII ISO
8859-1 symbols, the command
(load-library "iso-ascii")
will cause accented characters to be displayed comme {,c}a. If your
keymap does not make it easy to produce non-ASCII characters, then
(load-library "iso-transl")
will make the 2-character sequence Ctrl-X 8 a compose character, so
that the 4-character sequence Ctrl-X 8 , c produces c-cedilla. Very
inconvenient.
The command
(iso-accents-mode)
will toggle ISO-8859-1 accent mode, in which the six characters ', `,
", ^, ~, / are dead keys modifying the following symbol. Special com­
binations: ~c gives a c with cedilla, ~d gives an Icelandic eth, ~t
gives an Icelandic thorn, "s gives German sharp s, /a gives a with
ring, /e gives an a-e ligature, ~< and ~> give guillemots, ~! gives an
inverted exclamation mark, ~? gives an inverted question mark, and ''
gives an acute accent. This is the default mapping of accents. The
variable iso-languages is a list of pairs (language name, accent map­
ping), and a non-default mapping can be selected using
(iso-accents-customize LANGUAGE)
Here LANGUAGE can be one of "portuguese", "irish", "french",
"latin-2", "latin-1".
Since the Linux default compose character is Ctrl-. it might be
convenient to use that everywhere. Try
(load-library "iso-insert.el")
(define-key global-map [?\C-.] 8859-1-map)
The latter line will not work under xterm, if you use emacs -nw, but
in that case you can put
XTerm*VT100.Translations: #override\n\
Ctrl <KeyPress> . : string("\0308")
in your .Xresources.)
B. For less, put LESSCHARSET=latin1 in the environment. This is also
what you need if you see \255 or <AD> in man output: some versions of
less will render the soft hyphen (octal 0255, hex 0xAD) this way when
not given permission to output Latin-1.
C. For ls, give the option -N. (Probably you want to make an alias.)
D. For bash (version 1.13.*), put
set meta-flag on
set convert-meta off
set output-meta on
into your $HOME/.inputrc.
E. For tcsh, use
setenv LANG US_en
setenv LC_CTYPE iso_8859_1
If you have nls on your system, then the corresponding routines are
used. Otherwise tcsh will assume iso_8859_1, regardless of the values
given to LANG and LC_CTYPE. See the section NATIVE LANGUAGE SYSTEM in
tcsh(1). (The Danish HOWTO says: setenv LC_CTYPE ISO-8859-1; stty
pass8)
F. For flex, give the option -8 if the parser it generates must be
able to handle 8-bit input. (Of course it must.)
G. For elm, set displaycharset to ISO-8859-1. (Danish HOWTO: LANG=C
and LC_CTYPE=ISO-8859-1)
H. For programs using curses (such as lynx) David Sibley reports: The
regular curses package uses the high-order bit for reverse video mode
(see flag _STANDOUT defined in /usr/include/curses.h). However,
ncurses seems to be 8-bit clean and does display iso-latin-8859-1
correctly.
I. For programs using groff (such as man), make sure to use -Tlatin1
instead of -Tascii. Old versions of the program man also use col, and
the next point also applies.
J. For col, make sure 1) that it is fixed so as to do
setlocale(LC_CTYPE,""); and 2) put LC_CTYPE=ISO-8859-1 in the
environment.
K. For rlogin, use option -8.
L. For joe,
metalab.unc.edu:/pub/Linux/apps/editors/joe-1.0.8-linux.tar.gz is said
to work after editing the configuration file. Someone else said: joe:
Put the -asis option in /isr/lib/joerc in the first column.
M. For LaTeX: \documentstyle[isolatin]{article}. For LaTeX2e:
\documentclass{article}\usepackage{isolatin} where isolatin.sty is
available from ftp.vlsivie.tuwien.ac.at/pub/8bit.
A nice discussion on the topic of ISO-8859-1 and how to manage 8-bit
characters is contained in the file grasp.insa-
lyon.fr:/pub/faq/fr/accents (in French). Another fine discussion (in
English) can be found in rtfm.mit.edu:pub/usenet-by-
group/comp.answers/internationalization/iso-8859-1-charset.
If you need to fix a program that behaves badly with 8-bit characters,
one thing to keep in mind is that if you have a signed char type then
characters may be negative, and using them as an array index will
fail. Several programs can be fixed by judiciously adding (unsigned
char) casts.
13. X
This FAQ/HOWTO is about the Linux keyboard and console, not about X,
which substitutes its own handling. However, it seems useful to
document some of the Linux keyboard and console related properties of
X.
First of all, when X is started (say using startx or xinit) it opens
the first unused console, unless the desired console has been
indicated explicitly, as in xinit -- vt12. Note that this will fail
when there is no device file /dev/tty12, but that it will not fail
when the indicated console was in use already. When X finishes, it
will return to the original console. While it is running one can use
Ctrl-Alt-Fn to switch to VTn.
The XFree86 keymap mechanism is much poorer than the Linux mechanism.
For each keycode there are at most 4 symbols defined, namely for the 4
keymaps plain, shift, mod, mod+shift. What is the modifier mod? It is
the one designated by the symbol Mode_switch. For example, the
command xmodmap keys.dk, where the file keys.dk contains
keycode 64 = Mode_switch
keycode 113 = Mode_switch
keycode 38 = a A aring Aring
keycode 26 = e E ae AE
keycode 32 = o O oslash Ooblique
will make both Alt keys into mod keys, so that Alt+a gives å (a-ring),
etc. (Note the illogical naming of oslash and Ooblique.) Such an
xmodmap command can be placed in the .xinitrc shell script that is
executed by default when X is started.
13.1. What precisely does XFree86-2.1 do when it initializes its
keymap?
Since version 2.1, XFree86 will initialize its keymap from the Linux
keymap, as far as possible. However, Linux had 16 entries per key (one
for each combination of the Shift, AltGr, Ctrl, Alt modifiers) and
presently has 256 entries per key, while X has 4 entries per key (one
for each combination of Shift, Mod), so some information is
necessarily lost.
First X reads the Xconfig file, where definitions of the LeftAlt,
RightAlt, RightCtl, ScrollLock keys as Meta, ModeShift, Compose,
ModeLock or ScrollLock might be found - see X386keybd(1), later
XFree86kbd(1).
For Mod the LeftAlt key is taken, unless RightCtl was defined as
ModeShift or ModeLock, in which case RightCtl is taken, or RightAlt
was so defined, in which case RightAlt is taken. This determines how
the 4 XFree86 meanings of a key are selected from the 16 Linux
meanings. Note that Linux today does not distinguish by default
between the two Ctrl keys or between the two Shift keys. X does
distinguish.
Now the kernel keymap is read and the usually obvious corresponding X
bindings are made. The bindings for the "action keys" Show_Memory,
Show_State, Show_Registers, Last_Console, Console_n, Scroll_Backward,
Scroll_Forward, Caps_On and Boot are ignored, as are the dead
diacriticals, and the locks (except for ShiftLock), and the "ASCII-x"
keys.
Next, the definitions in the Xconfig file are used. (Thus, a
definition of Compose in Xconfig will override its value as found in
the Linux keymap.)
What happens to the strings associated with the function keys?
Nothing, X does not have such a concept. (But it is possible to define
strings for function keys in xterm - note however that the window
manager gets the keys first.)
I don't know how to convince xterm that it should use the X keymap
when Alt is pressed; it seems just to look at its resource
eightBitInput, and depending on whether that is true or false either
set the high order bit of the character, or generate an additional
Escape character (just like setmetamode(1) does for the console).
14. Unusual keys and keyboards
The two keys PrintScrn/SysRq and Pause/Break are special in that they
have two keycodes: the former has keycode 84 when Alt is pressed
simultaneously, and keycode 99 otherwise; the latter has keycode 101
when Ctrl is pressed simultaneously, and keycode 119 otherwise.
(Thus, it makes no sense to bind functions to Alt keycode 99 or Ctrl
keycode 119.) The Pause/Break key is also special in another way: it
does not generate key-up scancodes, but generates the entire
6-scancode sequence on key-down.
If you have strange keys, that do not generate any code under Linux
(or generate messages like "unrecognized scancode"), and your kernel
is 1.1.63 or later, then you can use setkeycodes(1) to tell the kernel
about them. Once they have gotten a keycode from setkeycodes, they can
be assigned a function by loadkeys.
For example, using showkey -s one sees that Microsoft keyboards use
the scancode sequences (in hexadecimal) e0 5b (left Windows key), e0
5c (right Windows key), e0 5d (Menu key). Microsoft Internet keyboard
also uses e0 6a (Back), e0 69 (Forward), e0 68 (Stop), e0 6c (Mail),
e0 65 (Search), e0 66 (Favorites), e0 32 (Web/Home), e0 6b (My
Computer), e0 21 (Calculator), e0 5f (Sleep). Use dumpkeys to see
what keycodes are still unused. Typically values like 89-95 and
112-118 and 120-127 are free. Now
% setkeycodes e05b 125
% setkeycodes e05c 126
% setkeycodes e05d 127
assigns keycodes to these scancode sequences, and
% loadkeys
keycode 125 = Decr_Console
keycode 126 = Incr_Console
keycode 127 = KeyboardSignal
%
would make these Windows keys go to the previous or next virtual con­
sole, and let the Menu key create a fresh virtual console (in case you
have something like spawn_console running).
14.1. Funkeys
Many modern keyboards have buttons or keys with labels like "Vol Up",
"Eject" etc. that suggest actions rather than strings. Of course one
can bind shell commands to them, but then they'll work only when you
are at a shell prompt. Rick van Rein wrote a package funkey
consisting of a kernel patch and a daemon. The kernel patch creates a
new character device, and adds a new key type to indicate which
keystrokes should be sent to this new character device. A daemon can
now listen to the character device, somewhat like gpm listens to the
mouse device, and perform the actions indicated in its config file.
See rick.vanrein.org/linux/funkey.
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 func­
tions 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. You can say
% loadkeys
keymaps 0-15
keycode 54 = SShift
keycode 97 = SCtrl
keycode 100 = SAlt
%
to make the right Shift, Ctrl, Alt sticky versions of the left ones.
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
15.2. Sticky keys under X
The following text was contributed by Piotr Mitros.
XFree86 supports an accessibility option which allows disabled users
to type single-handed. With sticky keys enabled, the user can hit a
modifier key (ctrl, alt, shift) followed by another key, rather than
having to hold the modifier key while hitting the letter.
To enable sticky keys, first make sure the xkb extension is enabled
(this is done during initial X server configuration and is usually
enabled by default). Next, run the X server with the +accessx option.
If you use startx, either run startx -- +accessx or add +accessx to
the serverargs line in the startx script. If you use xdm, add
+accessx to the appropriate server line in /etc/X11/xdm/Xservers.
It is also possible to enable X accessibility with some end-user
utilities with a running X server.
Once X accessibility is enabled, press the shift key five times in a
row to enable sticky keys. To disable sticky keys, either press the
shift key five times again, or press a key while holding a modifier
key.
XFree86 also supports Slow Keys, Repeat Keys, Bounce Keys and an
audible bell. xkbcomp can be used to generate a .xkm file to enable
these. The appropriate xkbcomp commands are listed in
/usr/X11R6/lib/X11/xkb/compat/accessx. Unfortunately, the exact
process is still undocumented.
16. Changing the video mode
As far as I know there are 6 ways to change resolution:
1. At compile time: change the line
SVGA_MODE= -DSVGA_MODE=NORMAL_VGA
in /usr/src/linux/Makefile.
1A. After compilation: use rdev -v - a terrible hack, but it exists.
2. At boot time: put vga=ask in the lilo config file, and lilo will
ask you what video mode you want. Once you know, put vga=mypreference.
3. At run time: A. Use the resizecons command. (This is a very
primitive wrapper around the VT_RESIZE ioctl.) B. Use the
SVGATextMode command. (This is a less primitive wrapper around the
VT_RESIZE ioctl.)
4. Not "on the console": Under dosemu, or with svgalib etc. you can
change the hardware video mode without the console driver being aware
of it. Sometimes this is useful in getting resizecons or SVGATextMode
set up: use dosemu and some DOS program to get into the desired
videomode, dump (say from another VT) the contents of all video
hardware registers, and use that in the initialization that resizecons
and SVGATextMode require. In some cases where the video mode has
gotten into some unusable state, starting dosemu, relying on the BIOS
to set up the video mode, and then killing dosemu (with kill -9), is
the easiest way to get into shape again.
16.1. Instructions for the use of resizecons
Get svgalib and compile the program restoretextmode. Boot up your
machine in all possible video modes (using vga=ask in the lilo config
file), and write the video hardware register contents to files CxR
(C=cols, R=rows), e.g., 80x25, 132x44, etc. Put these files in
/usr/lib/kbd/videomodes. Now resizecons 132x44 will change videomode
for you (and send SIGWINCH to all processes that need to know about
this, and load another font if necessary).
At present, resizecons only succeeds when there is memory enough for
both the old and the new consoles at the same time.
17. Changing the keyboard repeat rate
At startup, the Linux kernel sets the repeat rate to its maximal
value. For most keyboards this is reasonable, but for some it means
that you can hardly touch a key without getting three copies of the
corresponding symbol. Use the program kbdrate(8) to change the repeat
rate, or, if that doesn't help, edit or remove the section
______________________________________________________________________
! set the keyboard repeat rate to the max
mov ax,#0x0305
xor bx,bx ! clear bx
int 0x16
______________________________________________________________________
of /usr/src/linux/[arch/i386/]boot/setup.S.
Scott Johnston (sj@zule.com) reports: `To program the repeat rate of a
Gateway AnyKey keyboard all one has to do is press the "Repeat Rate"
key, then a function key F1-F8, then "Repeat Rate" again. F1 is the
slowest possible repeat rate, and F8 is really fast. If you somehow
manage to mess up your AnyKey keyboard doing this, simply press Ctrl-
Alt-SuspndMacro to reset your keyboard to factory default settings.'
18. Scrolling
There are two ways to get a screen to scroll. The first, called `hard
scrolling', is to leave the text in video memory as it is, but change
the viewing origin. This is very fast. The second, called `soft
scrolling', involves moving all screen text up or down. This is much
slower. The kernel console driver will write text starting at the top
of the video memory, continuing to the bottom, then copy the bottom
part to the top again, and continue, all the time using hard scrolling
to show the right part on the screen. You can scroll back until the
top op the video memory by using Shift-PageUp (the grey PageUp) and
scroll down again using Shift-PageDown (the grey PageDown), assuming a
default keymap. The amount of scrollback is thus limited to the
amount of video memory you happen to have and you cannot increase this
amount. If you need more scrollback, use some program that buffers
the text, like less or screen - by using a buffer on disk you can go
back to what you did last week. (One can set the amount of scrollback
for xterm by adding a line like XTerm*saveLines: 2500 in .Xresources.)
Upon changing virtual consoles, the screen content of the old VT is
copied to kernel memory, and the screen content of the new VT is
copied from kernel memory to video memory. Only the visible screen is
copied, not all of video memory, so switching consoles means losing
the scrollback information.
Sometimes, hard scrolling is undesirable, for example when the
hardware does not have the possibility to change viewing origin. The
first example was a Braille machine that would render the top of video
memory in Braille. There is a kernel boot-time option no-scroll to
tell the console driver not to use hard scrolling. See bootparam(7).
19. Screensaving
setterm -blank nn will tell the console driver to blank the screen
after nn minutes of inactivity. (With nn = 0, screensaving is turned
off. In some old kernels this first took effect after the next
keyboard interrupt.)
The s option of xset(1) will set the X screensaving parameters: xset s
off turns off the screensaver, xset s 10 blanks the screen after 10
minutes.
The video hardware powersaving modes can be enabled/disabled using the
setvesablank program given in the starting comment of
/usr/src/linux/drivers/char/vesa_blank.c.
20. Screen dumps
setterm -dump N will dump the contents of the screen of /dev/ttyN to a
file screen.dump in the current directory. See setterm(1).
The current contents of the screen of /dev/ttyN can be accessed using
the device /dev/vcsN (where `vcs' stands for `virtual console
screen'). For example, you could have a clock program that displays
the current time in the upper right hand corner of the console screen
(see the program vcstime in kbd-1.04.tar.gz). Just dumping the
contents goes with cat /dev/vcsN. These device files /dev/vcsN do not
contain newlines, and do not contain attributes, like colors. From a
program it is usually better to use /dev/vcsaN (`virtual console
screen with attributes') instead - it starts with a header giving the
number of rows and columns and the location of the cursor. See
vcs(4).
21. Some properties of the VT100 - application key mode
: Sometimes my cursor keys or keypad keys produce strange codes?
When the terminal is in application cursor key mode the cursor keys
produce Esc O x and otherwise Esc [ x where x is one of A,B,C,D.
Certain programs put the terminal in application cursor key mode; if
you kill them with kill -9, or if they crash, then the mode will not
be reset.
% echo -e '\033c'
resets all properties of the current VC. Just changing the cursor
application key mode is done by
% echo -e '\033[?1h'
(set) and
% echo -e '\033[?1l'
(clear).
When the terminal is in application keypad key mode the keypad keys
produce Esc O y and otherwise Esc [ z ~ for certain y and z.
Setting application keypad key mode is done by
% echo -e '\033='
and
% echo -e '\033>'
clears it again.
22. Hardware incompatibility
Several people have noticed that they lose typed characters when a
floppy disk is active. It seems that this might be a problem with
Uni-486WB motherboards.
Tjalling Tjalkens (tjalling@ei.ele.tue.nl) reports very similar
problems with "a no-brand GMB-486 UNP Vesa motherboard with AMD
486DX2-66 CPU" - during floppy activity some keystrokes are lost,
during floppy tape streamer (Conner C 250 MQ) activity many keystrokes
are lost.
Some people experience sporadic lockups - sometimes associated to hard
disk activity or other I/O.
Ulf Tietz (ulf@rio70.bln.sni.de) wrote: `I have had the same problems,
when I had my motherboard tuned too fast. So I reset all the timings
( CLK, wait statements etc ) to more conventional values, and the
problems are gone.'
Bill Hogan (bhogan@crl.com) wrote: `If you have an AMI BIOS, you might
try setting the Gate A20 emulation parameter to "chipset" (if you have
that option). Whenever I have had that parameter set to any of the
other options on my machine ("fast", "both", "disabled") I have had
frequent keyboard lockups.'
There may be a relation between keyboard problems and the video card
in use.
Shawn K. Quinn (skquinn@wt.net) wrote: `I have a Zeos Pantera
Pentium-90 that originally came with a Diamond Stealth 64 S3-based
video card. Under X I frequently got q's inserted into my text (how
annoying) especially if I typed very fast (during Netrek for instance,
even more annoying because guess what that does :-( ). Switching to a
Creative Labs Graphics Blaster MA202 solved the problem. I'm assuming
the Stealth 64 did something funny with the timings.'
23. Copyright
Copyright (c) 1993-2001 by Andries Brouwer. This document may be
distributed under the terms set forth in the LDP license at
http://metalab.unc.edu/LDP/COPYRIGHT.html or
ftp://www.win.tue.nl/pub/linux/LDP/COPYRIGHT.txt.
Additions and corrections are welcome. Andries Brouwer - aeb@cwi.nl
Reference in New Issue View Git Blame Copy Permalink