Hi Nicolasd,

POSIX::RT::Spawn also works, a suggestion made here. Unfortunately, POSIX::RT::Spawn doesn't capture the error string (for example command not found). Well, two solutions this one using POSIX::RT::Spawn and the other using MCE::Child with MCE::Channel.

spawn:

The system command by the main process fails like before, but not syscmd calling spawn.

use strict;
use warnings;

use POSIX::RT::Spawn;

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

    local ($?, $!);
    my $pid = spawn $cmd, @_;
    waitpid $pid, 0;

    my ($status, $errmsg) = ($?, $!);
    
    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;
    }
}

# My CentOS VM has 4 GB of RAM

# create big hash
my $memory_eaten = 3 * 1024*1024*1024 / 2; # 3 GB, adjust to fit
my %memory_eater = (
    foo => scalar( ' ' x $memory_eaten ),
);

# pass command and optionally args
syscmd('ls');  # this one works; see status that it succeeded
system('ls');  # this one fails; no ls output the 2nd time

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

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

# busy loop, see top output in another terminal
# notice the memory consumption (i.e. RES)
# press Ctrl-C to exit or let it finish
1 for 1..3e8;

[download]

output:

ls output from spawn
SYSTEM: ls exited with status 0
SYSTEM: something exited with status 127
SYSTEM: sleep exited with status 0

[download]

Regards, Mario

In reply to Re^5: System call doesn't work when there is a large amount of data in a hash (testing) 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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