Re: Bash spews bracketed-paste escape sequences when handling signal.

[microsuxxor]

On Wed, Dec 18, 2024, 10:40 PM Kaz Kylheku <kaz@kylheku.com> wrote:

> On 2024-12-18 12:48, Chet Ramey wrote:
> > On 12/18/24 1:27 PM, Kaz Kylheku wrote:
> >
> >> What remains is the question why I somehow cannot get my
> >> stuff to work with a different signal like SIGUSR1 or SIGVTALRM.
> >>
> >> Bash will not take them while it's sitting in the call to readline.
> >
> > Something is indeed messed up in your execution environment.
> >
> > Let's try killing an interactive shell sitting in readline() from another
> > terminal:
> >
> > $ echo $BASH_VERSION
> > 5.2.37(6)-release
> > $ trap
> > $ echo $$
> > 30762
> > User defined signal 1: 30
> >
> > [shell terminates]
> >
> > Now let's try killing an interactive shell that's not sitting in
> readline()
> > with the same fatal signal:
> >
> > $ echo $BASH_VERSION
> > 5.2.37(6)-release
> > $ trap
> > $ kill -USR1 $$
> > User defined signal 1: 30
> >
> > [shell terminates].
>
> Right; I didn't make the wrong claim that SIGUSR1 isn't fatal. I made
> that wrong claim only about SIGALRM, and retracted that already.
>
> The real issue is this:
>
> Let's work with SIGUSR1 first:
>
>   $ trap 'echo USR1' USR1
>   $ kill -USR1 $$
>   USR1
>   $ kill -USR1 $$
>   USR1
>
> So far, so good! Now let's sit at the prompt, while sending the signal
> from a background process:
>
>   $ while sleep 1; do kill -USR1 $$; done &
>   [1] 22261
>   $ fg
>   USR1
>   while sleep 1; do
>       kill -USR1 $$;
>   done
>   ^C
>   USR1
>

try

p=$$ ; while sleep 1 ; do kill -USR1 "$p" ; done &
try also trap - USR1 in the new process ( the while loop )

I waited 20 seconds before typing "fg". Nothing!
>
> Now, let's try it with SIGALRM:
>
>   $ trap 'echo ALRM' ALRM
>   $ while sleep 1; do kill -ALRM $$; done &
>   [1] 21882
>   $ ALRM
>   ALRM
>   ALRM
>   ALRM
>   ALRM
>   ALRM
>   ALRM
>   ALRM
>   ALRM
>
> The "echo ALRM" commands go off like clockwork, every second.
>
> Most likely because of the way Readline treats signals, SIGARLRM ends up
> "blessed" for this purpose. By dumb luck, I had picked the winning signal;
> it was the first one I reached for.
>
> I understand that Bash will die if you send a SIGUSR1, and it
> has no trap set up for it; but when it does have a handler set up,
> it seems that Readline may be blocking the signal (perhaps via the
> sigprocmask
> or whatever). I probably won't be digging into it more.
>
>
>
>
>
>