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Proc::Simple store return from background process

by perldarren (Novice)
on Oct 11, 2012 at 15:47 UTC ( #998484=perlquestion: print w/replies, xml ) Need Help??
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' ) } );

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.


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Re: Proc::Simple store return from background process
by Perlbotics (Chancellor) 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 { ...
    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.

      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;
      Thank you very much for your help.

      Regards, Darren

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