Consistent BackSpace and Delete Configuration
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Pico=20
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The keymapping problem can be traced back to the time when computers = used=20 punched tapes. The only way to correct a wrongly punched character was = to punch=20 additional bits in the tape (or rather, punch additional bits _out_ of = the=20 tape). Characters with all the bits punched were treated as deleted = characters.=20 See 'man ascii' for a list of the ASCII characterset, you'll see that = DEL,=20 (octal 177, decimal 127 and hexadecimal 7F) is the one with all the bits = punched=20 in (the ASCII code with the highest value). To be able to overwrite a = character=20 it is necessary to undo the feed between the characters first. For this = the=20 ASCII BS (octal 010, decimal 8, hexadecimal 08) was used. So to erase = the=20 last-typed character, you would have to press first BS to move back one=20 character, and then DEL to delete the character. In newer computers = either BS or=20 DEL was chosen to move back and delete in one press.
The question to use BS or DEL was (and is...) just a matter of = choice, just=20 as different operating systems chose different ways to represent = newlines, which=20 was done by first issuing a carriage return (CR) and then a line-feed = (LF). UNIX=20 chose ASCII LF (hexadecimal 0A) to do both at the same time, Macintosh = chose CR=20 and MS-DOS both. Unfortunately, in the BS-DEL case, Linux ended up with = two=20 possibilities.
The essential point in this issue is to go for one way consistently. =
This=20
page describes a way to consistently use DEL to erase the previous =
character,=20
the page called
At this point the best way to fix the keys on your machine is to =
install
If you miss an application on this page, it's either because the keys = are ok=20 in the application ("If it ain't broken, don't fix it"), or because I = don't know=20 about it. In either case, don't hesitate to mail me about it.
Throughout this document, = [<---]=20 and [Delete] are used to denote the physical keys on the keyboard, the = things=20 you actually press to erase characters. There are a few things to keep = in mind:=20 ASCII values can be represented in several equivalent ways. This means = that=20 ASCII BS is equivalent to 010 in octal, 8 in decimal and 08 in = hexadecimal=20 notation. To show that a number is in hexadecimal notation '0x' is put = in front=20 of it. Finally it should be noted that BS and DEL are known to = applications by=20 their corresponding control sequences. To sum it up:=20| Note: |
|---|
| ASCII BS =3D=3D 0x08 =3D=3D ^H |
| ASCII DEL =3D=3D 0x7f =3D=3D 0177 =3D=3D=20 ^? |
The reason the keys = (generally) do=20 not work out-of-the-box is partly lack of configuration (as you will see = later,=20 simply creating
.inputrc/.cshrc already helps a lot) and a =
more=20
difficult issue which I will try to describe below.=20
The linux console emulates a vt220 terminal which has the following=20 key-mapping:
Linux console/VT220 Key KeySymName Console characters -------------------------------------------------- Ctrl+H ---> Control_H ---> ASCII BS (0x08) [<---] ---> Backspace ---> ASCII DEL (0x7f) [Delete] ---> Delete ---> "\e[3~"Note 1: BS (0x08) is equivalent to ^H, which is left to be used by = applications (e.g. for help menus in emacs, but it could be anything). = DEL is=20 equivalent to ^?, or 0177 (octal) and 0x7f (hex) and "\e[3~" will show = up in=20 your xterm (using the
VT100 -- Key KeySymName Console characters -------------------------------------------------- Ctrl+H ---> Control_H ---> ASCII BS (0x08) [<---] ---> Backspace ---> ASCII DEL (0x7F)Now here's how xterm emulates the VT100 terminal:
Xterm's emulation of VT100 Key KeySymName Console characters -------------------------------------------------- Ctrl+H ---> Control_H ---> ASCII BS (0x08) [<---] ---> Backspace ---> ASCII BS (0x08) [Delete] ---> Delete ---> ASCII DEL (0x7F)It may be clear that by default the keys are mapped differently on = the=20 console and in xterm. This would be ok if it weren't for the fact that = while on=20 the console ^H is free to be used by applications, in an xterm it is not = (instead it's mapped to the [<---] key). Differences between terminal = types=20 are generally dealt with by the terminfo database (see below), mapping = terminal=20 specific strings to the correct key. However, in this case, the ^H = should=20 not be mapped. Terminfo is not enough, the settings of = the=20 terminal (xterm) have to be modified such that ^H is not used.=20
In my = previous=20 attempt at working around the problem, I put most of my effort in = trying to=20 map all keys to suit xterm's vt100 emulation. However, I now propose = another way=20 to deal with the problem. This basically means getting xterm to work = with the=20 consoles' default settings: [<---] will do ASCII DEL (0x7F, or ^?), = and=20 [Delete] will do "\e[3~". This way ^H is not used for any terminal = specific=20 functions, it can be used by applications.
There is no = clear=20 solution, but there are some pretty good work-arounds. What is needed is = to tell=20 xterm = how to=20 handle the keys, and then to tell other applications about it (i.e. how = xterm=20 handles the keys). The terminfo database contains descriptions of how = all kinds=20 of terminals handle (terminal specific) keys. Applications look at the = TERM=20 variable, and then search the corresponding database for the value of a = certain=20 key, e.g. the left-arrow key, and find the string that corresponds to = it. This=20 means that the strings in the database had better correspond to your = current=20 xterm settings. This involves modifying xterm's terminfo entry.=20When you change the keymapping on your own system, you may have =
problems when=20
accessing other systems. Luckily, this can be worked-around by a script =
which=20
changes the input it receives to the output that is expected by the =
application=20
(telnet, rlogin). See the
|
Environment |
Configuration=20
=
files |
Configuration | |
|
user |
| ||
- |
=
terminfo &=
nbsp; |
=
infocmp/tic &nbs=
p; | |
~/.Xdefaults (*) |
/etc/X11/Xresources |
xrdb ~/.Xdefaults (*) | |
- /etc/X11/xinit/.Xmodmap (**) xmodmap .Xmodmap | |||
~/.inputrc |
/etc/inputrc |
export INPUTRC=3D/etc/inputrc | |
~/.cshrc |
/etc/cshrc |
bindkey=20
(shellcommand) |
.Xresources**
/etc/X11/XF86Config also =
affects the=20
keyboard settings under X=20
This is often a problem. = When you=20 find that the keys are fine in e.g. vi on the console, but not in an = xterm (or=20 vice versa, or both) it means that your xterm-settings do not correspond = to the=20 settings listed in the terminfo database. I am not really comfortable = with=20 telling you to fiddle with terminfo, please be careful, make backups! If = you run=20 the tic command on the modified de-compiled terminfo entry as root, your = system's terminfo database will be modified automagically. Put the = original file=20 in a save place so you can run tic on it and restore the original state. = Read=20 the manpage. First try it as non-privileged user. You can start with = testing a=20 modified xterminfo file (see below) as explained, however, since these = are=20 likely to differ from your system's entry at other points, it's probably = better=20 to modify your own instead. At any rate, first find out whether the = terminfo=20 entry for xterm is in accordance with your xterm settings: =
infocmp | grep kbs
kbs=3D\177. This =
means DEL=20
(or ^?) is mapped to the backspace key, which is what we want. =
infocmp | grep kdch1
kdch1=3D\E[3~. This means =
that \E[3~=20
is mapped to the delete key. Often you will find kbs=3D^H and/or =
kdch1=3D\177, or=20
there will be no kdch1 at all. You can either edit the terminfo entry as =
described on the kdch1=3D\E[3~ and =
kbs=3D\177,=20
but make a backup first!) or you could download (click shift or right) a =
modified debian=20
xterminfo or redhat=20
xterminfo and test it. Put the file in =
~/.terminfo/x/xterm (for=20
testing purposes) and do for bash: export =
TERMINFO=3D~/.terminfo
setenv TERMINFO ~/.terminfo
echo =
$TERM
/etc/terminfo/x/xterm
/usr/lib/terminfo/x/xterm
The xterm (and friends) only = needs little=20 configuration. In the
/etc/X11/Xresources or=20
~/.Xdefaults (or wherever it's merged with the other =
xresources)=20
add the line: *VT100.Translations: #override \
<Key>BackSpace: string(0x7F)\n\
<Key>Delete: string("\033[3~")\n\
<Key>Home: string("\033[1~")\n\
<Key>End: string("\033[4~")
*ttyModes: erase ^?=20
Rxvt only uses Xresources if it is compiled with this =
option.=20
Since rxvt uses readline, to get home and end to work you will have to =
edit=20
.inputrc, see the
Putting xterm or nxterm in front of=20
*vt100.translations makes the settings specific for xterm =
or=20
nxterm. Sometimes this does not seem to work properly, in that case try =
using=20
both nxterm*VT100.Translations and=20
xterm*VT100.Translations.
1. The syntax of the Xresources files is very strict, =
make sure=20
you don't leave blank spaces after the backslash on each line. Also =
watch the=20
newline (\n\) sequences, there shouldn't be one at the last =
line of=20
an entry.
2. The sections are named, if you only use=20
*VT100.Translations it will work for all xterm and =
friends.
3.=20
For info about Xresources and other X related stuff refer =
to 'man =
X'.
If you use
/etc/X11/XF86Config. It is enable by default, =
so it=20
should be okay. Note the different keyboard layout-options. Now XFree86 =
will=20
translate the console mapping, and everything should work in X. If you =
have=20
problems, or want to fiddle with additional characters and things, =
create an=20
Xmodmap. Also if you want the keyboard to generate special=20
characters in X, xmodmap can also be used to configure the=20
function-keys. This is adequately described in the manual page =
('man=20
xmodmap'. Make sure that the following lines are included in your =
Xmodmap:=20
keycode 22 =3D BackSpacekeycode 107 =3D =
Delete
Note that the keycodes in X are not the same as in a =
VT. Use=20
showkey to see the keycodes generated by the keyboard in a =
VT, and=20
xev in X. There is an excellent graphical front end for =
X-keyboard=20
configuration: xkeycaps. Refer to the
Another way of generating special characters in X (without using=20
xmodmap) is by defining a Compose-key (for use as a "dead =
key") in=20
XF86Config in the Keyboard section:
=
RightCtl Compose
LC_CTYPE=3Diso-8859-1 (see 'man=
=20
XF86Config' if you want to know more. Note: =
this=20
doesn't seem work rxvt.Alternatively, owners of a windows keyboard = (one with=20 extra buttons, it need not be a M$ natural keyboard) can enable the=20
XKEYBOARD extension (enabled per default) in=20
XF86Config and uncomment the line (follow the instructions =
in the=20
file): XkbModel "microsoft"=20
Yet another way to use "dead keys" in X is by installing a modified =
version=20
of libX11 which includes support for dead keys (transparent for all =
apps).=20
First, get the modified version of libX11 (make sure you get the right =
version,=20
if you use glibc replace both libX11, ELF-libc5 and ELF-libc6). Now, =
deactivate=20
the XKB extension of XFree86 (edit XF86Config and run =
xmodmap on a=20
Xmodmap file with dead keys like dead_acute, dead_grave, dead_cedilla,=20
dead_ogonek and a Multi_keys one too.
A special case is if you use xdm, you need to deactivate XKB from the =
/etc/X11/xdm/Xservers file, passing a -kb parameter to the =
server=20
like this:
:0 local /usr/X11R6/bin/X -kb
/etc/X11/xdm/Xsetup_0 file add a line to load =
the=20
Xmodmap, like this: if [ -r /etc/X11/xinit/.Xmodmap ]; then
/usr/X11R6/bin/xmodmap /etc/X11/xinit/.Xmodmap
fi
More Composing Talk
A problem common to all compose schemes is = that=20 while some composing systems make more sense than others, none of them = make all=20 of the iso_8859_1 characters readily accessible, simply because it is = impossible=20 to remember the combinations for all characters. So instead of, or in = addition=20 to getting special libraries, it is often desirable to simply have a = list of=20 characters you can copy from, a poor man's iso_8859_1 table so to speak. = Just=20 grab you favorite editor, open a file called iso_8859_1 (or any other = name, but=20 check the name and path) and put in all iso_8859_1 characters. Wait, = here they=20 are (you may want to create a different order):=A1 =A2 =A3 =
=A4 =A5 =A6 =A7 =A8 =A9 =AA =AB =AC =AE =AF =B0 =B1 =B2 =B3 =B4 =
=B5 =B6 =B7 =B8 =B9 =BA =BB =BC =BD =BE =BF =C0 =C1 =C2 =C3 =C4 =C5 =C6 =
=C7
=C8 =C9 =CA =CB =CC =CD =CE =CF =D0 =D1 =D2 =D3 =D4 =D5 =D6 =D7 =D8 =D9 =
=DA =DB =DC =DD =DE =DF =E0 =E1 =E2 =E3 =E4 =E5 =E6 =E7 =E8 =E9 =EA =EB =
=EC =ED =EE
=EF =F0 =F1 =F2 =F3 =F4 =F5 =F6 =F7 =F8 =F9 =FA =FB =FC =FD =FE =FF=20
/usr/local/lib. =20
#!/bin/bash=20
export LESSCHARSET=3Dlatin1=20
exec xterm -T Iso_8859_1-TABLE -geometry 77x4 +sb -bg SteelBlue -fg =
white \
-fn lucidasanstypewriter-bold-12 -e less /usr/local/lib/iso_8859_1
/etc/man.config, and =
change=20
the following line: NROFF /usr/bin/groff -Tascii =
-mandoc
NROFF /usr/bin/groff -Tlatin1 -mandoc
Create a file, /etc/inputrc for system wide use or=20
~/.inputrc for personal use. Actually, this is the readline =
initialization file, readline is a library that some programs (bash, =
kvt) use to=20
read input (try bind -v to see a list of readline key and =
function=20
bindings). Cut and paste the following in the file to make the Delete =
key delete=20
characters under the cursor, and make Home and End work as =
well:
"\e[3~": delete-char
# this is actually equivalent to "\C-?": delete-char
# VT
"\e[1~": beginning-of-line
"\e[4~": end-of-line
# kvt
"\e[H":beginning-of-line
"\e[F":end-of-line
# rxvt and konsole (i.e. the KDE-app...)
"\e[7~":beginning-of-line
"\e[8~":end-of-line
/etc/inputrc was created, add the =
following=20
line to /etc/profile: export =
INPUTRC=3D/etc/inputrc
Make sure that the stty erase character is set to ^?. =
Type
stty -a | grep erase
and check if it says
erase =3D ^?;
If it is set to something else (e.g. ^H) then put the =
following=20
line in both .bashrc and in either =
.bash_profile or=20
/etc/profile:
if tty --quiet ; then
stty erase '^?'
fi
.Xdefaults: =
*ttyModes: erase ^?
=20
If you create /etc/inputrc, note that Bash will ignore=20
~/.inputrc (currently this happens in all distributions =
except=20
Debian, however, this might change in the future). As an alternative, =
you can=20
edit ~/.inputrc, and copy this to /etc/skel/, =
so it's=20
in the home directories of all new users.
Push the key-combination=20
'Ctrl-x-r' (push the control-key, the x-key. release it, =
push the=20
r-key, release it, and then release the control-key) to see if the =
changes in=20
inputrc take effect. Or just login again, and it will work. =
You can also change the keybindings on the fly with the =
bind=20
command, e.g:
[localhost]> bind "\C-?": backward-delete-charThis is useful to test different keybindings, if they work you can = put=20 them in
~/.inputrc. Read all about it in the readline =
manpage.=20
People using keymaps with e.g. Scandinavian characters who would like =
bash to=20
display these characters (=F8l;-) have to add the following lines in=20
.inputrc:set convert-meta offset =
output-meta onset input-meta on
For more =
info,=20
check the Danish-H=
OWTO.
If you use the tcsh shell, put the = following=20 lines in your
/etc/cshrc or your personal ~/.cshrc=20
file: #.cshrc
if ($term =3D=3D "xterm" || $term =3D=3D "vt100" \
|| $term =3D=3D "vt102" || $term !~ "con*") then
# bind keypad keys for console, vt100, vt102, xterm
bindkey "\e[1~" beginning-of-line # Home
bindkey "\e[7~" beginning-of-line # Home rxvt
bindkey "\e[2~" overwrite-mode # Ins
bindkey "\e[3~" delete-char # Delete
bindkey "\e[4~" end-of-line # End
bindkey "\e[8~" end-of-line # End rxvt
endif
[localhost]> source .cshrc
For programs = using the=20 Athena widgets (xpaint, xbmbrowser, xman, xmh, xedit, pixmap, bitmap,=20 editres...) put the following in
.Xdefaults to get Delete =
to work: *Text.translations: #override \=20
~Shift ~Meta <Key>Delete: delete-next-character()
x-win.el in the =
emacs=20
root directory, and find the following:
;; Map certain keypad keys into ASCII characters
;; that people usually expect.
(define-key function-key-map [backspace] [127])
(define-key function-key-map [delete] [127])
(define-key =
function-key-map [delete] [deletechar])
(define-key function-key-map =
[delete] [deletechar])
(define-key global-map [home] `beginning-of-line)
(define-key global-map [end] `end-of-line)
~/.emacs make these keys move you to the =
beginning=20
and end of the current line. Note that the M-< and M-> keybindings =
remain=20
untouched and can still be used to go to the beginning and end of the =
buffer.=20
First find the file joerc. It is =
most likely=20
/usr/lib/joe/joerc, but sometimes /etc/joerc, =
or maybe=20
even /usr/local/lib/joerc. Try 'locate joerc' =
if you=20
can't find the file. Make a backup for safety, or copy it to .joerc in =
your home=20
directory, and change/add the following lines in the section "Standard =
JOE user=20
interface" in joerc: bol ^[ [ H # =
Standard xterm escape seq.
bol ^[ [ 1 ~ # Standard VT escape seq.
bol ^[ [ 7 ~ # rxvt
eol ^[ [ F # Standard xterm escape seq.
eol ^[ [ 4 ~ # Standard VT escape seq.
eol ^[ [ 8 ~ # rxvt
'man=20
joe'. BTW, these modifications apply to jpicorc, =
jstarrc and jmacsrc as well.=20
KDE provides=20
a new alternative to kvt called konsole. To get the home/end keys to =
work in=20
konsole you have to put: =20
"\e[H":beginning-of-line
"\e[F":end-of-line
in .inputrc. Additionally, make sure that you have =
checked=20
the 'BS sends DEL' checkbox (right mouse click, or through =
the=20
'Options' pulldown menu). In kvt, KDE's home=20
and end can be configured by editing ~/.inputrc =
(tcsh=20
users too, it uses readline): =20
"\e[H":beginning-of-line
"\e[F":end-of-line
Less is ok on some systems. If it =
is not on=20
yours, try the following. Create a file, /etc/lesskey, for=20
system-wide use. This will be a lesskey input file. Put the =
following lines in the file: #line-edit
\e[3~ delete
\e[1~ home
\e[4~ end
Save the file, and compile it as follows: =
[localhost]> lesskey -o /etc/less /etc/lesskey
Add the following line to /etc/profile:
export =
LESS=3D"-MM -k/etc/less"
Now type:
[localhost]> . /etc/profile
By fiddling with these settings you should be able to get less to =
accept (all=20
of) the holy keycodes, at least, it works on my computer. For some =
exciting=20
reading, check 'man=20
lesskey'.
~/.Xdefaults: nedit.remapDeleteKey: =
False
Save the file, and the next time you start ~/.nedit, but every time you save the default settings, =
the=20
.nedit file will be overwritten, and you'll have to (n)edit =
it=20
again.
Note the nedit, as e.g. netscape, is a motif application. This means = that it=20 uses the XKeysymDB, see thet netscape section.
The keys should be ok, as = long as=20 the XKeysymDB is installed in one of the places where netscape looks = (where=20 netscape itself is installed, or/usr/X11R6/lib/X11/). =
XKeysymDB is=20
similar to an xmodmap file, but with a very cryptic and poorly =
documented=20
syntax. Luckily, it does do the delete/backspace thing right, so no =
sweat.=20
If you use xmodmap, you may want to check out the graphical front end =
for=20
X-keyboard configuration: xkeycaps. Get the .rpm at
keycode 22 =3D BackSpace
keycode 107 =3D Delete
alternatively, you can put it in e.g. your .Xclients file, or in=20
/etc/X11/xdm/Xsetup_0):
# map the [<---] =
key to the [BackSpace] keysym.
xmodmap -e "keycode 22 =3D BackSpace"
# map the [Delete] key to the [Delete] keysym.
xmodmap -e "keycode 107 =3D Delete"
.Xdefaults modifications. If you use the =
~/.inputrc to=20
get Delete to work in xterms (and then pico and pine will be able to use =
Delete), however, this creates problems with other apps (e.g. joe) which =
cannot=20
be easily solved because joe relies on the .Xdefaults =
modifications=20
to get the keys right. Anyway, it turns out that #!/usr/bin/expect
eval spawn -noecho $argv
interact {
\177 {send "\010"}
"\033\[3~" {send "\004"}
}
picofix pico
.pinerc and find the following =
lines:=20
# Specifies the program invoked by ^_ in the Composer,
# or =
the=20
"enable-alternate-editor-implicitly" feature.
editor=3D
You can enter the command for any editor here, e.g. joe =
or=20
vi.
If you want the editor to be started right away, start =
pine,=20
enter SETUP and Config and select the=20
enable-alternate-editor-implicitly option. Now the editor =
of choice=20
will be started automagically when you start writing a message.
Pico fans may want to try jpico, which is basically joe with pico =
keybindings=20
(and all the extra's joe offers). Others my be even smarter and switch =
to Ctrl-j-trick, =
the=20
latter can use pine keybindings.
:help fixdel in vim and =
read all=20
about it.=20
Put the following line in=20
~/.muttrc: bind editor <delete> delete-charThis will make [Delete] do its job in
#!/usr/bin/expect
eval spawn -noecho $argv
interact {
\177 {send "\010"}
"\033\[3~" {send "\177"}
}
kbdfix =
telnet=20
brokenhost. Thanks to Philip Hands for this clever workaround.=20
The logical next step is to automate the trick. Create a file,=20
/etc/broken-backspace-hosts (or a shorter name...). In this =
file,=20
list the hosts which expect ^H and ^? instead of ^? and ^[[3~. Now you =
can make=20
a wrapper for telnet as shown below. This particular script assumes that =
the=20
telnet binary has been renamed telnet.orig, and that the kbdfix script =
described=20
in the previous section is somewhere in your =
path):
#!/bin/sh
if grep -wq "$@" /etc/broken-backspace-hosts ; then
exec kbdfix telnet.orig "$@"
else
exec telnet.orig "$@"
fi
- The = Linux Keyboard and Console HOWTO=20
- Consistent Keyboard Configuration' article (
Danish-H= OWTO=20Tcsh=20 documentation=20- Fixkeys = Mini=20 Howto=20
Bash=20 documentation'man=20 X'=20'man= =20 XF86Config'=20'man=20 lesskey'=20'man=20 joe'- Dead keys = under=20 X11
- Consistent Keyboard Configuration' article (
This document was put together by Anne=20 Baretta (anne@ibb.net). Please mail me if you find mistakes, = tY-pO's,=20 alternative or plain better solutions. A few people have already pointed = out=20 many mistakes (there simply cannot be that many left...), which improved = the=20 document a lot. I=20 would like to thank all the people who contributed to the page, and = Thomas=20 Telkamp for hosting the site.
![3D"page](3D"http://www.nedstat.nl/cgi-bin/nedstat.gif?name=3Dkeyboardtel")