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.
% 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 characters
are enclosed between \ and /.
If echoe is not set, then the erase char is echoed
(which is reasonable when it is a printing character, 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.
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.
At the first attempt, you are talking to getty. At the second attempt,
you are talking to login, a different program.
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.
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.
(i) Because the VT100 had a Delete key above the Enter key.
(ii) Because Linus decided so.
% 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).
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.
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 deletion 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)
Put in your .kermrc file the lines
set key \127 \8
set key \8 \127
XTerm*VT100.Translations: #override\n\
<KeyPress> BackSpace : string(0x7f)\n\
<KeyPress> Delete : string(0x08)\n
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.
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)
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.
Ted Kandell (ted@tcg.net) suggests the following:
Somewhere in your .profile add the following:
stty erase ^HIf you are using
bash, add the following lines to your .inputrc:
"\C-?": delete-char "\C-h": backward-delete-charAdd 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.
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".
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 .Xresourcesin
.xinitrc, and you are settled.
For a much more extensive discussion of these things, and alternative solutions, see Anne Baretta's page.