I try to make a script that run three child process an return some information, when all child process finish, i need to continue with a parent process, with the information returned by the childrens, but i have soooo manyyy problems becouse i can't understand on my mind, how works the fork function, perhaps somebody help me with that, anyway, i developed this script on windows but i'm use or i hope use on linux.

when i test the script, return this:

Child 1 -> -3334

Child 2 -> -4564

parent process

Child 3 -> -4365



yes, on windows return negative process id.

On windows at least the signal CHLD or CLD not work, (but both are defined in %SIG hash),

i say that, becouse, if i do something like SIG{CHLD} = sub { print "it's work"; }; nothing happen, it's correct? why?, in fact if i use something like:

sub REAPER { # don't work almost on windows
        while (($child = waitpid(-1,WNOHANG)) > 0) {}
        $SIG{CHLD} = \&REAPER;
}

$SIG{CHLD} = \&REAPER;

[download]


the result of the script it's the same, why?, what wrong i do? to replace this i put three waitpit but nothing change, what can i do?

To set the priority i tried to use setpriotity, but it's not implement on windows yet,

on linux, work?

one interesting thing, if i use three wait; the script work fine, but i try to do the right,

i don't know why work with that and don't work with the other.

well nothing more for now

thank you 

use POSIX ":sys_wait_h"; 

$|=1;

#$pid=fork(); # when i use setpriority i call a fork here and replace 
+below in the if sentence.

#$pid1=fork();

#$pid2=fork();

#setpriority($$,0); # not implement on windows :-(

#setpriority($pid,1);
#setpriority($pid1,2);
#setpriority($pid2,3);

my %CHILD = ();

sub REAPER { # don't work almost on windows
        while (($child = waitpid(-1,WNOHANG)) > 0) {}
        $SIG{CHLD} = \&REAPER;
}

$SIG{CHLD} = \&REAPER; 

# if i do something like $SIG{CHLD} = sub { print "it's work"; };
# well ... nothing happen, why?

if (!($CHLD{1} = fork())) { # when use setpriority i replace "if (!($C
+HLD{1} = fork())) {" to "if (!$pid) {"

    print "child 1 -> $$\n";

    sleep 2; # other small thing, why this sleep don't work here and s
+leep the parent process?

    exit;    # but only for 2 seconds, if i have three sleep with 2 se
+conds 2*3 = 6 seconds,
             # itn't it? yeah yeah i'm lost ;-(

}

if (!($CHLD{2} = fork())) {
    print "child 2 -> $$\n";
    sleep 2;
    exit;
}

if (!($CHLD{3} = fork())) {
    print "child 3 -> $$\n";
    sleep 2;
    exit;
}

# if i replace $CHILD{1} with -1... dosen't work :-(
# obviusly, when i use this i don't use the signal $SIG{CHLD}

# if i only put one waitpid... well don't work

#waitpid $CHILD{1}, WNOHANG; # if i put wait; the script work fine
#waitpid $CHILD{2}, WNOHANG; # wait;
#waitpid $CHILD{3}, WNOHANG; # wait;
print "parent process\n";

[download]

Edited by planetscape - added code tags and line breaks

In reply to forks, how do that? by apolo

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