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Getting Delete and Backspace to work just right is nontrivial,
especially in a mixed environment, where you talk to console,
to 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
5.1 How to tell Unix what character you want to use to delete the last typed character
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 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
into ~/.inputrc .
`Getty used to do the right thing with DEL and BS but is broken now?'
Earlier, the console driver would do BS Space BS
(
`Login behaves differently at the first and second login attempts?'
At the first attempt, you are talking to
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
and under X use
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
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
Many distributions have a
`How do I get a dvorak keyboard?'The command
will give you a dvorak layout, probably by loading
something like /usr/lib/kbd/keymaps/i386/dvorak/dvorak.map.gz .
Under X , put
in XF86Config .
`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
Or, if you just want the Backspace key to generate a BackSpace:
Or, if you just want the Delete key to generate a 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
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
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
Recent versions of emacs have a function keyboard-translate
and one may simplify the above to
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
5.6 How to tell kermit to interchange Delete and Backspace
Put in your
5.7 How to tell xterm to interchange Delete and Backspace
5.8 How to tell xterm about your favourite tty modes
Normally xterm will inherit the tty modes from its invoker.
Under
in /usr/lib/X11/app-defaults/XTerm or in
$HOME/.Xresources , assuming that you have a line
in your $HOME/.xinitrc or $HOME/.xsession .
5.9 How to tell non-Motif X applications that the Del key deletes forwardPut
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
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 ( Somewhere in your .profile add the following:
If you are using bash , add the following lines to your .inputrc :
Add the following lines to your .xinitrc file:
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 solutionThere 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
in .Xresources , and
in .xinitrc , and you are settled.
For a much more extensive discussion of these things, and alternative solutions, see Anne Baretta's page.
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