Get parent process to handle signals for its children?

slaniel has asked for the wisdom of the Perl Monks concerning the following question:

I have a script that calls out to a number of other scripts via system(). When I Ctrl+C any of the child processes, I want the parent process to handle that SIGINT. The problem is that when I Ctrl+C one of the child processes, the child process gets killed and we return to the flow of control in the parent process -- which then moves on to the next system() call. Instead, I want the parent process to die. The hack way to do this is to set the appropriate signal handler in each of the child scripts:

$SIG{'INT'} = sub { kill -9, getppid() };
[download]

which sends SIGKILL to the process's parent. But of course that doesn't scale: every time I create a new script, I'll have to add that handler in it. And if the parent process happens to not be the parent script -- e.g., if the parent process is a login shell -- that 'kill -9, getppid' has just killed my login shell. So what's the approach here, if I want the parent process to handle all the signals for its children?

Comment on Get parent process to handle signals for its children? Download Code

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Re: Get parent process to handle signals for its children? by ikegami (Patriarch) on Jul 12, 2006 at 18:53 UTC
Why don't you simply check how the child died before running the next `system` call? Refer to `system`'s return value.	[reply] [d/l] [select]
Re^2: Get parent process to handle signals for its children? by Hue-Bond (Priest) on Jul 12, 2006 at 19:08 UTC
For example, doing something along this lines: `while (1) { print "sleeping\n"; system 'sleep', 2; warn "system: $!" if -1 == $?; my $signal_caught = $? & 127; die "Child got a SIGINT" if 2 == $signal_caught; }` [download] -- David Serrano	[reply] [d/l]
Re^3: Get parent process to handle signals for its children? by slaniel (Acolyte) on Jul 12, 2006 at 19:10 UTC
Oh, I see! I had forgotten about `$?`. That seems to get me most of the rest of what I want. Beautiful! Thanks so much for the clarification.	[reply] [d/l]
Re^2: Get parent process to handle signals for its children? by runrig (Abbot) on Jul 12, 2006 at 19:12 UTC
Have you heard that kill -9 can be a dangerous thing? Update: Oops. This post was more directed at the OP rather than ikegami.	[reply]
Re^2: Get parent process to handle signals for its children? by slaniel (Acolyte) on Jul 12, 2006 at 19:08 UTC
That's certainly a good approach that gets me 90% of what I want. I'd still like to know whether the parent can handle signals for its children. It would also be nice to get more specific information than just `system(foo) != 0`; it would be nice to know that `system()` died when it handled a SIGINT. Is that doable?	[reply] [d/l] [select]
Re^3: Get parent process to handle signals for its children? by ikegami (Patriarch) on Jul 12, 2006 at 19:13 UTC
The value returned by system is composed of three fields. The exit value of the subprocess is `$rv >> 8`, `$rv & 127` gives the signal (if any) from which the process died, and `$rv & 128` reports whether or not there was a core dump.	[reply] [d/l] [select]