See also %SIG

Ok, my bad, it seems you should be able to do what you tried (I've just never done it that way). Perhaps someone else can shed light on this.

--
I'd like to be able to assign to an luser

You're suffering from buffering. You'll see output if you use print "You can't kill me!\n"

Tutorials: Input and Output: Suffering from Buffering?

Thanks that worked perfectly. I should have remembered that from my c++ experience.

sub interrupt
{
   my $sig_name = shift;
   print "You can't kill me! $sig_name caught";
}
[download]

there is no need for "$SIG{"INT"} = "interrupt";" within interrupt() subroutine.

Interesting, because perlipc documents it this way:

or better still:

use POSIX ":sys_wait_h";
sub REAPER {
    my $child;
    # If a second child dies while in the signal handler caused by the
    # first death, we won't get another signal. So must loop here else
    # we will leave the unreaped child as a zombie. And the next time
    # two children die we get another zombie. And so on.
    while (($child = waitpid(-1, WNOHANG)) > 0) {
        $Kid_Status{$child} = $?;
    }
    $SIG{CHLD} = \&REAPER; # still loathe SysV
}
$SIG{CHLD} = \&REAPER;
# do something that forks...
[download]

So, has perl's behaviour changed (when?), is one of SIGINT, SIGCHLD special for perl, or is perlipc simply out-of-date?

Alexander

--
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)

Nothing to do with Perl.

Some system remove the handler once it has caught a signal. If you want your program to handle more than one instance of the signal on those platforms, you need to set the handler again in the handler.

I don't know what those systems are. Not your everyday systems. I think it's "SysV" systems, whatever that means.

Starting with 4.3BSD and System V Release 3, signal handlers remain installed after a signal occurs. So, yes, the requirement to re-install a signal handler is some super ancient (many decades ago) stuff. No modern system and no POSIX compliant system will cause an installed signal handler to be affected. I would think that the Perl docs should be updated.

Now, this while() loop in the reaper is definitely needed! Signals are not "queued" for delivery. When a signal occurs, always interpret that to mean "at least one and maybe more than one of this signal has occurred".

Update: Wiki ATT releases SVR3, SVR4. SVR3 was GA'ed in 1986. I figure after 25 years, we don't have to worry much about R2 any more!