use strict;
use warnings;

use IO::Pipe;

$SIG{PIPE} = sub {exit;};

print qq{Parent PID $$\n};
my $pipeFH = IO::Pipe->new();

my $pid;
if ($pid = fork)
{
    $pipeFH->writer();
    print qq{Kid is PID $pid\n};
}
elsif(defined($pid))
{
    $pipeFH->reader();
    sleep 1 for 1 .. 100;
    exit;
}

while ((my $returnPid = wait) != -1)
{
    print qq{Kid $returnPid returned\n};
}
[download]

Maybe there is a flaw in my attempt.

Cheers,

JohnGG

Update: The flaws in my attempts were twofold. Firstly, frodo72 pointed out that the SIGPIPE would not be generated until the child process tried to do I/O on the pipe that had been closed at the other end because the parent had been killed. Secondly, it appears that IO::Pipe is somehow consuming the SIGPIPE before the child sees it so the child carries on oblivious to it's parent's death. Again, frodo72 discovered this by refactoring my code to use pipe instead of IO::Pipe.

frodo72 ++ and thanks for all the help.

IIRC the SIGPIPE signal should be sent only when the one end tries to do I/O on a pipe that is closed on the other end. Moreover... why sleep 1 for 1 .. 100; instead of sleep 100;?

Flavio
perl -ple'$_=reverse' <<<ti.xittelop@oivalf

Don't fool yourself.

Why the sleep 1 for 1 .. 100;? My ignorance really; I wasn't sure whether the script, like my daughter, would sleep through the alarm so I decided to try lots of small sleeps after it didn't work with one long sleep.

I was already trying things like explicitly closing the pipe in the parent if it caught a signal. Following your post I have modified the script so the child keeps printing a "heartbeat" to the pipe but still to no avail. Here's the modified script.

use strict;
use warnings;

use IO::Pipe;
my $pipeFH;

my $rcHandler = sub {$pipeFH->close(); exit;};

$SIG{INT} = $rcHandler;
$SIG{QUIT} = $rcHandler;
$SIG{TERM} = $rcHandler;

print qq{Parent PID $$\n};
$pipeFH = IO::Pipe->new();

my $pid;
if ($pid = fork)
{
    $pipeFH->reader();
    print qq{Kid is PID $pid\n};
}
elsif(defined($pid))
{
    $SIG{PIPE} = sub {exit;};
    $pipeFH->writer();
    $pipeFH->print(qq{Kid: Snoozing\n});
    for my $heartbeat ( 1 .. 30 )
    {
        $pipeFH->print(qq{Kid: Heartbeat $heartbeat\n});
        sleep 1;
    }
    
    $pipeFH->print(qq{Kid: Waking\n});
    print qq{Kid: Quitting\n};
    exit;
}

while ((my $returnPid = wait) != -1)
{
    print qq{Kid $returnPid returned\n};
}

while (defined(my $line = $pipeFH->getline()))
{
    print qq{Read: $line};
}
[download]

I had been killing the parent with a kill -15 (TERM) from another shell but I noticed that the child does go away immediately if I Ctrl-C the running parent. Is it the case that child processes also get an INT if the parent gets one from the shell?

Cheers,

JohnGG