Note again that the main issue that confuses people trying to fix
their system is that usually they are fixing thing in the wrong
place. Since the parts that work often just work by chance, trying to fix
the system assuming something is broken will often lead to change correct
settings into incorrect settings.
The first step towards a clean solution is to know exactly which
terminals are deviant and which not. Usually they all behave like the
console, and in this case the modifications to get everything working
are minimal. If, however, you have some deviant terminal (e.g., a
deviant version of gnome-terminal), you will
have to treat it in a special way.
The following C one-liner
void main(void) {int c; while(c = getchar()) printf("%d 0x%02X\n", c, c);} |
may help you. Put the line into a file named
ascii.c,
compile it with
gcc ascii.c -o ascii, type
./ascii and press a key followed by
RETURN.
The program will display the decimal and hexadecimal codes of the
ASCII sequence produced (you may want to do a
stty
erase ^- first to get really all the codes). Now you can easily see
what
Backspace key does: if it emits a
DEL
(127), you have a standard emulator, if it emits a
BS (8) you have
a deviant one.
If you have some deviant terminal emulator, you must distinguish
it from the standard ones. Theoretically, this should not be a problem
because there are different entries in the terminal database for
terminals with different sequences (the entry used depends on the value
of the TERM variable).
Here we take the approach that the gnome entry
should be used for all deviant VT100 emulators, and the
xterm entry for the standard ones. This is in line
with several distributions (except a few cases like RedHat ≤5.0,
where the xterm entry is deviant).
However, gnome-terminal uses by
default the same entry as xterm, so if one
is deviant and the other one is not you will need to find a way to tell
them apart. The option termname of
gnome-terminal allows the user to set the
TERM variable to a more sensible name. However, in older
versions of gnome-terminal the option does
not work. Moreover, sometimes it is not easy to modify the way
gnome-terminal is started.
A good idea here is to exploit the fact that
gnome-terminal sets the
COLORTERM variable to
gnome-terminal. Thus, by adding a simple test to the
shell configuration files we can fix the TERM
variable.
Our problem now is that the terminal database could lack a
gnome entry for deviant terminals (this happens on a
number of termcap and
terminfo versions). Recent
terminfo databases have an entry
gnome, but, in any case, since
gnome-terminal behaves essentially like
xterm modulo our famous two keys, it is
possible to automagically generate a brand new correct entry.
The readline library used by the
bash and by many other programs to read the
input line can be customized so to recognize specific sequences of
characters. The customization can also depend on the
TERM variable, so once we can distinguish terminals we
can do fine tuning of the keyboard.
Moreover, if you want less and other
application that do raw line input to work correctly, you must convince
the shell that under a deviant terminal emulator the erase character is
BS, and not DEL (in the other case
the Backspace key is already emitting
DEL, so we do not have to do anything). This can be
done using the command stty.
| These fixes have some drawbacks. First, they work only for the
specified terminals. Second, in theory (but this is unlikely to happen)
they could confuse the readline library on
other terminals. Both limitations are however mostly harmless. |
First of all, check with infocmp gnome
whether you already have a gnome entry in your
terminfo database (we will fix
termcap later). If the entry does not exist,
the following command
bash$ tic <(infocmp xterm |\
sed 's/xterm|/gnome|/' |\
sed 's/kbs=\\177,/kbs=^H,/' |\
sed 's/kdch1=\\E\[3~,/kdch1=\\177,/') |
will create a correct one in
~/.terminfo. If the same
command is launched by the root, it will generate the entry in the global
database (you can override this behaviour by setting
TERMINFO to
~/.terminfo). Note that if your
xterm
entry is already deviant (e.g., you have a Red Hat ≤5.0) the script will copy it unchanged, which is
exactly what we want.
Now, add the following snippet to
~/.inputrc[1]:
This line teaches the
readline library how to
manage your standard
Delete key for standard emulators,
and with a bit of luck it should not interfere with other
terminals. However, now we must also explain to the library the meaning
of the
DEL character on deviant terminals, for instance
by adding
$if term=gnome
DEL: delete-char
Meta-DEL: kill-word
"\M-\C-?": kill-word
$endif |
to
~/.inputrc. If
xterm
is deviant, too, you must add other three lines for it. On the other
hand, if no terminal emulator is deviant this part is not needed. All
these changes can be made global by altering the
/etc/inputrc file.
Note that the conditional assignments make deviant terminal
emulators work given that the TERM variable is
set correctly. To guarantee this, there are a number of
techniques. First of all, since the default value of the
TERM variable for
gnome-terminal is xterm, if
all terminals are not deviant then we do nothing. If, however, a terminal
that by default uses the xterm entry is deviant you
must find a way to set the TERM variable correctly; assume
for instance this is true of
gnome-terminal.
The simplest way to obtain this effect is to start
gnome-terminal with the argument
--termname=gnome, for instance by suitably setting the
command line in the launcher on the GNOME panel. If
however you have an old version, and this method does not work, you can
add the lines
if [ "$COLORTERM" = "gnome-terminal" ]
then
export TERM=gnome
fi |
to your
~/.bashrc configuration file
[2]. The assignment is executed
only under
gnome-terminal, and sets correctly the
TERM variable.
| Setting the terminal to gnome could prevent
ls from using colours, as many versions of
ls do not know that
gnome-terminal is colour capable. To avoid this
problem, create a configuration file ~/.dircolors with
dircolors --print-database >~/.dircolors, and add a line
TERM=gnome to the configuration file. |
We will now generate on-the-fly a suitable
termcap entry for deviant terminal emulators; this
can be done as follows, always in ~/.bashrc:
if [ "$TERM" = "gnome" ]
then
export TERMCAP=$(infocmp -C gnome | grep -v '^#' | \
tr '\n\t' ' ' | sed 's/\\ //g' | sed s/::/:/g)
fi |
Finally, we must explain to the terminal device which character is
generated by the erase key. Since usually the erase key is expected to
backspace, there is a nice trick taken from the Red Hat
/etc/bashrc that works: add this to
~/.bashrc:
KBS=$(tput kbs)
if [ ${#KBS} -eq 1 ]; then stty erase $KBS; fi |
It's a simple idea: we read from the terminal database the capability
kbs, and set the erase character to its value if it is a
single character (which happens in both standard and deviant terminals).
| Certain distributions could have fixes already in place in the
system-wide /etc/inputrc configuration file. In
this case you can eliminate redundant lines from your
~/.inputrc. |