Re: Should the readline *-meta flags reset when $LANG changes?

[Chet Ramey]

On 11/14/22 11:40 AM, Koichi Murase wrote:
> 2022年11月15日(火) 0:22 Chet Ramey <chet.ramey@case.edu>:
> > On 8/11/22 5:56 PM, Koichi Murase wrote:
> > > Can we also change the behavior of TERM in a similar way with option
> > > 4?  Currently, a temporal change of TERM clears keybindings of some
> > > keys (home, end, right, left, etc.) even when the temporal change does
> > > not survive across multiple calls of readline:
> >
> > I finally got back to look at this, and I couldn't reproduce it. That was
> > expected, since the arrow key binding functions are pretty careful not to
> > overwrite an existing binding. Then I figured out what was going on.
>
> Thank you for checking this.
>
> > > $ bash-dev --norc
> > > $ echo "$TERM"
> > > screen.xterm-256color
> > > $ bind '"\e[1~": bell'
> >
> > This unbinds the key sequence, since `bell' is not a valid bindable command
> > name.
>
> Ah, OK. The above ``reduced case'' was not correct, but unbinding is
> actually what I wanted to do in the original problem. In the original
> code, I intentionally unbind the keybinding for "\e[1~" and instead
> try to bind a single byte `\e'.

What do you try to bind \e to?

> However, after running "TERM=xxx
> infocmp" in the command line, the keybinding does not work anymore
> This is what I experienced. 

Well, yes, if you unbind it, restoring TERM will restore the original
binding.


> > I think the "TERM=$TERM" idiom to reset the readline terminal settings
> > without overwriting existing key bindings is useful enough to retain the
> > current behavior.
>
> I think it can be useful, but should that also apply to the tempenv of
> the form "TERM=$TERM infocmp"? 

You can't really have one without the other, given the way the special
variable handling works (and has worked).


> In the sense that the side effects of
> the temporary environment variables (tempenvs) are intended to be not
> persistent after the execution of the command (unless it is for
> special builtin and functions in the POSIX mode), I would like to
> request that the idiom TERM=$TERM to reset the terminal settings would
> not be invoked for the tempenvs.

The variables in the temporary environment are restored to their previous
values after the command executes. It's that restoration that triggers the
call to rl_reset_terminal(), not the environment assignment, undoing any
side effects of the environmnent assignment. Bash treats these uniformly,
whether the simple command is a builtin, function, or command from the
file system.

So from readline's perspective, there is no difference between TERM=xxx
and 'TERM=xxx command'. rl_reset_terminal() gets called the same way from
the same function in both cases.

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/