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From: Janis Papanagnou <janis_papanagnou+ng@hotmail.com>
Newsgroups: comp.unix.shell
Subject: Re: Initiate command in another shell session?
Date: Fri, 14 Mar 2025 03:41:47 +0100
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 <vqv1c0$3gq75$1@dont-email.me> <vqv7um$35n$1@reader1.panix.com>
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On 13.03.2025 19:25, Dan Cross wrote:
> In article <vqv1c0$3gq75$1@dont-email.me>,
> Janis Papanagnou  <janis_papanagnou+ng@hotmail.com> wrote:
>> [...]
> 
> I think I understand; let me paraphrase, and tell me if I'm
> correct?
> 
> [...paraphrase snipped...]

Yes, that was correct.

> 
> If that's correct, then the answer, generally is no: you can't
> do that.  If you open the pty device associated with that shell,
> you're and write to it, you're really writing to the same
> output that the shell process is connected to, not it's input.
> 
> There's no simple way to interpose onto the input stream.

My unformed thoughts went along the line of how a pty intercepts
communication to a process, probably combined with an attachment
to a process (as I recall you can attach a debugger to a running
process).

> [...]
>>
>> [*] Something I never noticed before, BTW. - My CPU% was at "0%",
>> not even the typical high basis load of Firefox was displayed. The
>> whole window manager stuff (mouse movement, menu item selection,
>> change of virtual sessions, switch to plain non-WM consoles, some
>> tools in the task-bar like the clock was still counting, etc.) was
>> working, though, but not a single (other) command got executed;
>> not even a new cursor shown when hitting <Enter> in a shell window.
> 
> Are you sure the issue wasn't with your keyboard?  I'd have
> maybe tried to disconnect and reconnect it.

I'm pretty sure it wasn't the keyboard(s). (At least I see no way
how it should have influenced that extreme effect. Both keyboards
are firmly attached, they worked smoothly many years, and still
did their job after the system restarts.) It could of course have
been some OS component handling the keyboards in principle, but
all the above described accompanied effects that I observed are
also unrelated to the keyboard. So at best very unlikely I'd say.
Anyway. After the reboot everything was fine, so I don't make my
mind about it. It was just something I've never observed before;
typically, if anything, my window manager (or other long running
processes) show problems occasionally after long uptimes, while
the rest works smoothly, but this time... just strange (to me).

Janis