CODEWITHSUNDEEP
perlfork
user2953575
user2953575

Reputation: 25

Kill child process created with fork

The following will output :

Start of script
PID=29688
Start of script
PID=0
Running child process 1
Done with child process
PID=29689
Start of script
PID=0
Running child process 1
Done with child process

It's working as intended, however I would like to kill the previous child PID.

How can a kill the PID of the child with out kiling the MAIN ?

Thank you !

my $bla = 1;

while (1) {

print "Start of script\n";
run_sleep();

}

sub run_sleep {

    sleep(3);
    my $pid = fork;

    return if $pid;     # in the parent process
    print("PID=" . $pid . "\n");
    print "Running child process " . $bla++ . "\n";
    exit(0);  # end child process

}

Upvotes: 1

Views: 1438

Answers (1)

Len Jaffe
Len Jaffe

Reputation: 3484

When you fork a child, and then fail to wait() on it, it will become a defunct process (a zombie in Unix parlance) when it exits. You'll notice that its parent process ID becomes 1, and it will not go away until the OS rebooted.

So the traditional pseudocode for forking looks something like this:

if ($pid = fork()) {
   # pid is non-zero, this is the parent
   waitpid($pid)   # tell OS that we care about the child

   do other parental stuff
}
else {
   # pid is 0 so this is the child process
   do_childish_things()
}

Your code doesn't do that, so you're probably getting zombies, and then getting frustrated that you can't get rid of them.

Upvotes: 2

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