Hi All,

I have been farting and fooling around with fork, and I was trying to see the time difference in having child processes create more child processes to complete a task vs the parent creating all the children. so here is what I did: 

#!/usr/bin/perl -w
use strict;
use Time::HiRes qw(usleep ualarm gettimeofday tv_interval);

open (FILE, ">testfork.txt");
my $runs = 33;
my $start = [gettimeofday];

while ($runs) {
        my $pid = fork;

        # Parent
        if ($pid) { $runs--; }

        # Child
        if ($pid == 0) {
                my $pid = fork;
                if ($pid == 0) {
                    my $pid = fork;
                    if ($pid == 0) {
                        print FILE "$runs\n";
                        exit;
                    }
                    print FILE "$runs\n";
                    exit;
                }
                print FILE "$runs\n";
                exit;
        }

}
my $elapse = tv_interval ($start);
close (FILE);

print "Elapsed time = $elapse\n";
exit;

[download]
This should create 99 lines in the output file and it does. I then change the code to:


#!/usr/bin/perl -w
use strict;
use Time::HiRes qw(usleep ualarm gettimeofday tv_interval);

open (FILE, ">testfork.txt");
my $runs = 99;
my $start = [gettimeofday];

while ($runs) {
        my $pid = fork;

        # Parent
        if ($pid) { $runs--; }

        # Child
        if ($pid == 0) {
#                 my $pid = fork;
#                 if ($pid == 0) {
#                     my $pid = fork;
#                     if ($pid == 0) {
#                         print FILE "$runs\n";
#                         exit;
#                     }
#                     print FILE "$runs\n";
#                     exit;
#                 }
                print FILE "$runs\n";
                exit;
        }

}
my $elapse = tv_interval ($start);
close (FILE);

print "Elapsed time = $elapse\n";
exit;

[download]


This should also create 99 lines in the output file, but consistently after 65 lines I get the following:

Use of uninitialized value in numeric eq (==) at testfork1.pl line 16.

I can not see why this is happening. Does this happen to anyone else running the code? If can anyone enlighten me on why?

Thank you all in advance,

Cameron

In reply to Uninitialized value in numeric eq (==) after 65 iteration of a loop using fork?!? by doowah2004

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