PHP Code:
$content = implode('', file('http://www.domain.com/sup.txt'));
$fp = fopen("file.txt", "w");
if ($fp) {
fwrite($fp, $content);
fclose($fp);
}
A simple one. It will write
http://www.domain.com/sup.txt to file.txt (owerwrite and truncate file.txt if it exist).