Hi again,

I made an improved version including worker sending the error message. Replace system with syscmd in your script. That sends the command along with any arguments to the background worker. The worker receives the command to run and any arguments. The status and error message are sent to the main process after running the command.

syscmd:

use strict;
use warnings;

use MCE::Child;
use MCE::Channel;

my $chnl = MCE::Channel->new( impl => 'Simple' );

# spin up worker early before creating big hash
mce_child {
    local $SIG{__WARN__} = sub {};
    while ( my ($cmd, @args) = $chnl->recv ) {
        local ($?, $!);
        system($cmd, @args);
        $chnl->send2($?, $!);
    }
};

sub syscmd {
    my $cmd = shift;
    return unless $cmd;

    $chnl->send($cmd, @_);
    my ($status, $errmsg) = $chnl->recv2;
    
    if ($status == -1) {
        print "SYSTEM: failed to execute ($cmd): $errmsg\n";
    }
    elsif ($status & 127) {
        printf "SYSTEM: $cmd died with signal %s, %s coredump\n",
            ($status & 127), ($status & 128) ? 'with' : 'without';
    }
    else {
        printf "SYSTEM: $cmd exited with status %d\n", $status >> 8;
    }
}

# create big hash
my %big_hash;

# pass command and optionally args
syscmd('ls');

# attempt to run a command not found
syscmd('something');

# sleep for 2 seconds
syscmd('sleep', '2');

# notify no more work, then reap worker
$chnl->end;
MCE::Child->waitall;

[download]

output:

ls output from syscmd
SYSTEM: ls exited with status 0
SYSTEM: failed to execute (something): No such file or directory
SYSTEM: sleep exited with status 0

[download]

Regards, Mario

In reply to Re^2: System call doesn't work when there is a large amount of data in a hash by marioroy
in thread System call doesn't work when there is a large amount of data in a hash by Nicolasd

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