China DOS Union

I want to make a batch file for multi-threaded downloading.
Curl can download in segments and then merge them, but I don't know how curl can get the file size in advance, and then calculate how many segments it needs to be split into?

If the OP means PHP's curl, you can look at this code:
$file_sizeofurl =
a_array['Content-Length'];
--------------------2. Use curl to get the size of a remote file
What if the server forbids get_headers?
Use another method, with curl.
I've always felt that curl is like a virtual user, able to imitate anything.

Below is a function from a foreigner
Please note
echo '
head-->'.$head.'<----end

';
I added this line, so I could see exactly what the header contains
function
remote_filesize($uri,$user='',$pw='')
{
// start output
buffering
ob_start();
// initialize curl with given uri
$ch =
curl_init($uri);
// make sure we get the header
curl_setopt($ch,
CURLOPT_HEADER, 1);
// make it a http HEAD request
curl_setopt($ch,
CURLOPT_NOBODY, 1);
// if auth is needed, do it here
if (!empty($user)
&& !empty($pw))
{
$headers = array('Authorization: Basic ' .
base64_encode($user.':'.$pw));
curl_setopt($ch, CURLOPT_HTTPHEADER,
$headers);
}
$okay = curl_exec($ch);
curl_close($ch);
// get the
output buffer
$head = ob_get_contents();
// clean the output buffer and
return to previous
// buffer settings
ob_end_clean();

echo '
head-->'.$head.'<----end
';

// gets you the numeric value from the Content-Length
// field in the http header
$regex = '/Content-Length:s([0-9].+?)s/';
$count = preg_match($regex, $head, $matches);

// if there was a Content-Length field, its value
// will now be in $matches[1]
if (isset($matches[1]))
{
$size = $matches[1];
}
else
{
$size = 'unknown';
}
//$last=round($size/(1024*1024),3);
//return $last.' MB';
return $size;
}

I'm using bat, not PHP, sorry.