Re: "wait" loses signals

[Denys Vlasenko]

On 2/19/20 9:30 PM, Chet Ramey wrote:
> On 2/19/20 5:29 AM, Denys Vlasenko wrote:
> > A bug report from Harald van Dijk:
> >
> > test2.sh:
> > trap 'kill $!; exit' TERM
> > { kill $$; exec sleep 9; } &
> > wait $!
> >
> > The above script ought exit quickly, and not leave a stray
> > "sleep" child:
> > (1) if "kill $$" signal is delivered before "wait",
> > then TERM trap will kill the child, and exit.
>
> This strikes me as a shaky assumption, dependent on when the shell receives
> the SIGTERM and when it runs traps.

The undisputable fact is that after shell forks a child
to run the "{...} &" subshell, it will receive the SIGTERM signal.

And since it has a trap for it, it should be run.

> (There's nothing in POSIX that says
> when pending traps are processed. Bash runs them after commands.)

Yes, and here we are "after command", specifically after "{...} &" command.
Since we got a trapped signal, we must run its trap.