On Wed, Nov 19, 2008 at 02:29:23PM -0500, Ted Unangst wrote:
> On Wed, Nov 19, 2008 at 12:16 PM, Jonathan Steel <[EMAIL PROTECTED]> wrote:
> > In the SIGCHLD signal handler of parent process, I need to get the pid of
> > the child when the child dies. To do this I'm using sigaction with the
> > SA_SIGINFO flag. But the siginfo_t->si_pid member does not seem to be set.
> >
> > I found the following post from Otto that seems to say that what I'm trying
> > to do may not work on OpenBSD.
> >
> > http://www.archivum.info/fa.openbsd.tech/2008-02/msg00124.html
>
> > Does anybody know how I'm to accomplish this, or why it doesn't work?
>
> I think the only way to go is to use wait() to get the child.
>
> >From one of the links:
> "The SA_NOCLDSTOP flag, when supplied in the act-> sa_flags parameter,
> allows overloading SIGCHLD with the System V semantics that each
> SIGCLD signal indicates a single terminated child. Most conforming
> applications that catch SIGCHLD are expected to install
> signal-catching functions that repeatedly call the waitpid() function
> with the WNOHANG flag set, acting on each child for which status is
> returned, until waitpid() returns zero. If stopped children are not of
> interest, the use of the SA_NOCLDSTOP flag can prevent the overhead
> from invoking the signal-catching routine when they stop."
>
> Even if the pid were filled in, it would be a lot more work for the
> kernel to reliably shoot a single for every process that died, so you
> would have to loop on wait() anyway to cover the case where two
> children die before you act.
And what's more, a parent should call wait(2) anyway to avoid creating
zombies.
-Otto
