Forking sub inside a module

vbruno has asked for the wisdom of the Perl Monks concerning the following question:

I am new to the perl fork function, and I am not sure that it does what I am looking for.

I have 2 long running subs. Sub1 I only want to run serially, sub2 I would like to fork off and not wait for a return. Here is psuedocode to illustrate (in my current implementation that has no forking):

#! /usr/local/bin/perl

use Mod1;
use Mod2;

my @nodes = ("switch1", "switch2", "switch3", "switch4", "switch5");

foreach my $node_name (@nodes) {

   # a 4-10 minute TL1 conversation using Expect
   my $port_hashref = Mod1->sub1($node_name); 

   # a five minute series of SQL queries using DBI
   Mod2->sub2($node_name, $port_hashref);

}
[download]

I do not want to wait for sub2 to finish on a switch name before moving on to sub1 on the next switch name. I do not care about a return value from sub2.

With my limited understanding of fork, I expect it will fork the entire program instead of my sub2 code block and that it won't be easy to pass in my hash ref to sub2 after the fork.

Any ideas on how to do this (with or without fork)?

Comment on Forking sub inside a module Download Code

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Re: Forking sub inside a module by JavaFan (Canon) on Jun 15, 2009 at 16:03 UTC
The entire process will be forked, but both forks will continue running from the point the process forked. And since the data is also forked (copied), there's no problem. You'll get something like: `foreach my $node_name (@nodes) { my $port_hashref = Mod1->sub1($node_name); my $pid = fork; die "Unable to fork: $!\n" unless defined $pid; unless ($pid) { # Child process. Mod2->sub2($node_name, $port_hashref); exit; # When done, child should terminate. } } 1 while -1 != wait; # Reap children.` [download]	[reply] [d/l]
Re^2: Forking sub inside a module by vbruno (Novice) on Jun 15, 2009 at 16:18 UTC
Oh, that isn't so hard! I was thinking the forked process would start over at the beginning. I am not clear on the last line. I understand that I will want to wait for the last child to finish before exiting the parent, but is there a less obfuscated way of saying that?	[reply]
Re^3: Forking sub inside a module by ikegami (Patriarch) on Jun 15, 2009 at 18:00 UTC
There's nothing obfuscated there. Perhaps the `1` in void context is confusing you? It can be avoided as follows: `while (-1 != wait) {}` [download]	[reply] [d/l] [select]
Re^4: Forking sub inside a module by FloydATC (Deacon) on Jun 16, 2009 at 07:38 UTC
Re^5: Forking sub inside a module by admiral_grinder (Pilgrim) on Jun 16, 2009 at 13:20 UTC
Some notes below your chosen depth have not been shown here
Re: Forking sub inside a module by John M. Dlugosz (Monsignor) on Jun 15, 2009 at 17:48 UTC
You might also look at Perl Threads, available as of Perl 5.6. See the threads documentation.	[reply]