sub system_no_output {
    my $mode = shift;

    open(my $chld_in, '<&', *STDIN) or die($!);
    my $chld_out = '>&STDOUT';
    my $chld_err = '>&STDERR';

    open($chld_out=undef, '>', devnull()) or die($!)   if $mode & 1;
    open($chld_err=undef, '>', devnull()) or die($!)   if $mode & 2;

    my $pid = open3($chld_in, $chld_out, $chld_err, @_)
        or die($!);

    return waitpid($pid, 0);
}