How to tell Child wait till Parent kill it

[gjoshi]

Hi all

I need child to wait till it parent tell it to kill it. My requirement is:

I have parent which forks processes and all those child process has to do something and update database. Parent will check the status of the database and then decide whether to kill the child or not.

Any advice how to do it? I am not able to figure out the wait in child what it should be?

[blindluke]

In the child process, set up a signal handler. A standard kill sends out the TERM signal, but you can wait for any signal, and react accordingly. Here's an example:

use strict;
use warnings;

$SIG{HUP}  = \&sighup_handler;
$SIG{TERM} = \&sigterm_handler;

sleep(3600);

sub sigterm_handler {
    die "Caught TERM, will not do anything!";
}

sub sighup_handler {
    # commit changes to the database and exit
}

[gjoshi]

Hi Luke, I am not getting where in my code i have to do this and how to do this?

$SIG{HUP}  = \&sighup_handler;
$SIG{TERM} = \&sigterm_handler;

#----------------------------- MAIN ----------------------------
print "I am the only process.\n";
my @children_pids;


for my $count (1..3){
        my $child_pid = fork();
        print "PID: $child_pid \n";
        if ($child_pid) {  # If I have a child PID, then I must be the
+ parent
                push @children_pids, $child_pid;
        }
        else { # I am the child
                my $Child_PID = $$;
                print "CHILD's PID is: $Child_PID \n";
                #doing something
                # writing into DB
                sleep $wait_time;
        }
}

print "\n ----- Main DB ---- \n";
foreach my $child (@children_pids) {
        print "Parent: Waiting on $child\n";
        #check DB stats
        #send kill signal
        waitpid($child, 0);
}

thanks --girija