#!/usr/bin/perl
use warnings;
use strict;
use threads;

my $thr1 = threads->new(\&sub1);
my $thr2 = threads->new(\&sub2);
my $thr3 = threads->new(\&sub3);

my $ReturnData1 = $thr1->join;
print "Thread1 returned @$ReturnData1\n";

my $ReturnData2 = $thr2->join;
print "Thread2 returned @$ReturnData2\n";

my $ReturnData3 = $thr3->join;
print "Thread3 returned @$ReturnData3\n";

print "Press any key to exit\n";
<>;
############################################## 
sub sub1 {
my @values = ('Fifty-six','foo', 1);
  sleep 1;
 return \@values;
}
############################################## 

sub sub2 {
my @values = ('Forty-two','bar', 2);
  sleep 2;
 return \@values;
}
########################################## 
sub sub3 {
my @values = ('Sixty-six','baz', 3);
  sleep 3;
 return \@values;
}

# join() does three things: it waits for a thread to exit, 
# cleans up after it, and returns any data the thread may 
# have produced. 

Re^2: forks, how do that?

apolo

created: 2006-01-01 17:37:01

perlmonks

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prlmnks

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Ok, i try to get three page with lwp, in the "same" moment, i only think in fork function but you have reason, i don't know how to work theads but i'm test an tell you, anyway, if anyone know something about the forks problem, please tell me.

Well, thank you.

You may view the original node and the consideration vote tally.

You've got several issues going on. First, if you're using fork on Windows, you're really using Perl threads behind the scenes. See [doc://perlfork]. If you want to work with subprocesses on Windows, I recommend checking out [mod://Win32::Job]. As mentined above, getting data back from a fork is harder than getting it back from a thread -- you probably need to use some sort of external file or pipe. See [doc://perlipc]. If you're trying to do multiple child processes at the same time, you've got added complexity in handling returned data.

For managing multiple, forked processes in general, I've seen many recommendations for [mod://Parallel::ForkManager] as a cleaner interface. There's also a tutorial on it: [id://291446]. It looks like what you want can be boiled down to something like this (adapted from the docs for it):

use Parallel::ForkManager;

$pm = new Parallel::ForkManager($MAX_PROCESSES);

my @task_details = (
  # data needed for each sub-process
);

foreach my $task (@task_details) {
    $pm->start and next; # do the fork

    # do the sub process work using whatever details are in $task

    # write the results to a file somewhere, perhaps with a
    # pre-set name passed in $task

    $pm->finish; # do the exit in the child process
}
$pm->wait_all_children;

# Continue in parent and read in the results