用php调用ping命令

               
               
                ?php
// created by joe lumbroso
// see some other good php3 scripts
// goto http://www.dtheatre.com/scripts
echo "Pinging
";
$to_ping = "google.com";
$count = 3;
$psize = 65;
echo " Please be patient, this can take a few moments...\n
";
flush();
while (1) {
?>
    pre>
    ?
    exec("ping -c $count -s $psize $to_ping", $list);
    for ($i=0;$i  count($list);$i++) {
        print $list[$i]."\n";
    }
    ?>
    /pre>
?
    flush();
    sleep(3);
}
?>
exec功能这么强大，看来也必给系统带来不少安全隐患。