Proc::Simple store return from background process

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

Hi everybody, I would really appreciate some help with Proc::Simple.

I would like to use Proc::Simple to push an object method into the background ( If that is the correct way to term what I am doing ).

The Proc::Simple docs are really good, they just don't have an example exactly like my situation so my stupidity has unstuck me very quickly.

This is my code:

        my $status = $child_procs{$host}{proc}->start( sub { $return =
+ $hinst->evtwait(
                               GROUP   => $host_in_transit->{copy_grp}
+->{copy_grp},
                                MODE    => '22',
                                STATE   => 'good',
                                TIMEOUT => '9999'
                                ) } );
[download]

The trouble is that the process backgrounds nicely but I am unable to keep the value returned to $return. Any ideas how I can do this ?

Ultimately, I will run up to 5 of these processes in the background and will store the $return in a hash.

Thanks Everybody.

Regards,
Darren

Comment on Proc::Simple store return from background process Download Code

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Re: Proc::Simple store return from background process by Perlbotics (Archbishop) on Oct 11, 2012 at 18:27 UTC
Short answer: You cannot with Proc::Simple (longer: in your case when starting a sub{...} as a child process) This is what happens in the child part of the fork() that is executed for your `$func = sub{...};` `# in Proc::Simple # $func = sub{ ... }; # your code ... if(ref($func) eq "CODE") { $self->dprt("Launching code"); $func->(@params); exit 0; # Start perl subroutine } else { ...` [download] So, the `exit 0` (successful execution) is all that is returned from your sub{...}. The `$return` value is discarded. Your sub{...} could return the result to the main process by means of IPC or by storing the result in a temporary file (e.g. YAML, JSON, Storable, etc.). The parent process could read the result from a pipe or load the serialised data from a file after the sub has finished. Update: IPC::Lite However, I guess, that in this particular case, you're better off with threads and maybe a queue.	[reply] [d/l] [select]
Re^2: Proc::Simple store return from background process by perldarren (Novice) on Oct 12, 2012 at 10:34 UTC
Ok, I see. To get around this I made my routine physically exit with the return code I originally wanted to return. I can then read this as Proc::Simple intended using something like: `my $exit = $child_procs{myhost}{proc}->exit_status(); my $exit_code = $exit >> 8;` [download] Thank you very much for your help. Regards, Darren	[reply] [d/l]