sub detect_disk
{
    my ($flag, $dir) = @_; 
    my $available_space = `df $dir`;
    my @array = split(/\s+/, $available_space);
    $available_space = $array[10];

    if ($flag eq 'entry' and $available_space < 6000000)
    {   
        print ("NOTICE: The left space of $dir is $available_space (KB), please make sure enough space is available for the regresssion.\n\n");
    }   
    elsif ($flag eq 'routine' and ($available_space < 1000000))
    {   
        print ("NOTICE: The left space of $dir is $available_space (KB), regression will waiting!\n");
        sleep 60; 
        while ($available_space < 1000000)
        {
            # send_mail($mail_list, $report_title, $report_file);
            $available_space = `df $dir`;
            @array = split(/\s+/, $available_space);
            $available_space = $array[10];
            sleep 60; 
        }
    }   
}