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Re: Stopping subprocesses

by rowdog (Curate)
on Aug 25, 2010 at 23:26 UTC ( #857342=note: print w/ replies, xml ) Need Help??


in reply to Stopping subprocesses

What I really want to do is call B from another Perl script A, and A kills B (with system("kill PID") or whatever), thereby killing C as well.

One way to do that is to localize the HUP signal handler and then send a HUP signal to your process group. You can have A do

{ local $SIG{HUP} = 'IGNORE'; kill HUP => -$$; }

I've attached a proof of concept demo. Sorry there's no backport, I got lazy once I had it working.

a.pl
#!/opt/perl/bin/perl use 5.012; use warnings; say "A start"; my $pid; unless ( $pid = fork ) { die "cannot fork: $!" unless defined $pid; system("./b.pl"); sleep 30; exit; } sleep 2; say "A sending kill HUP -$$"; { local $SIG{HUP} = 'IGNORE'; kill HUP => -$$; } say "A waiting for lost children"; while (1) { my $kid = waitpid -1, 0; $kid == -1 and last; say "A reaped child $kid"; } say "A end";
b.pl
#!/opt/perl/bin/perl use 5.012; use warnings; say " B start"; my $pid; unless ($pid = fork) { die "cannot fork: $!" unless defined $pid; system("./c.pl"); sleep 30; exit; } say " B waiting on lost children"; while (1) { my $kid = waitpid -1, 0; $kid == -1 and last; say " B reaped child $kid"; } sleep 30; say " B end";
c.pl
#!/opt/perl/bin/perl use 5.012; use warnings; say " C start"; sleep 30; say " C exit";
output
$ ./a.pl A start B start B waiting on lost children C start A sending kill HUP -20682 A waiting for lost children A reaped child 20683 A end


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