Posted on 2000-02-22
Last Modified: 2010-03-05

While uploading a file from a form (using "file" type) can I get the size of the file ? Or perhaps the size that has been uploaded so far?
Question by:leoleo
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LVL 16

Expert Comment

ID: 2546159
yes you can..

try this...


<form ENCTYPE="multipart/form-data" action="/cgi-bin/" Method=POST>
Attach:<input name="doc" type="file">

use CGI;

$query=new CGI;


$WebFileName = "UpdateGroupFile.htm";
print "Content-type: text/html\n\n";

`rm /tmp/$WebFileName`;
open(MYFILE,"> /tmp/$WebFileName") || die $!;
binmode MYFILE;
  $size+=$bytesread; ## Keep track of file size
  print MYFILE $data;

`chmod 777 /tmp/$WebFileName`;

print "<B>$DocLocation has been uploaded</B><br>\n";
print "<B>Size = ",$size," byte(s)</B><BR>\n";

Expert Comment

ID: 2549578

Maneshr, your code is correct, but, what you get is actually the size *after* the file has already been uploaded (by and saved to temporary file.

So, you can get at the size of the file


OTOH, getting to know the size *before* uploading it, and limiting the upload, requires rummaging through the internals of, which goes out of its way to hide this kind of details. Gaining more control probably leads to overrriding's methods, and specifically the read_multipart sub (look for the UPLOADS: label).
Now that sorta breaks the incapsulation and code privacy stuff...;-)

Failing this, and if coarse grained control is sufficient, one can set the $CGI::POST_MAX variable  to some maximum byte value, and be assured that the *total* post size will not exceed that value.

As a final note, some clients make it possible to know the file size in the header of the multipart document (I.e., they set Content-Length on the single part). But that is client dependent and, last time I looked, netscape was not doing it, so it cannot really be relied upon.

Because of this, the only sure way to know if a file exceeds some specified length is to read that many bytes from stdin.

HTH & cheers,


Author Comment

ID: 2549582

Thanks, it worked.

One more thing: Is there absolutely no way of getting the total file size just as upload starts? So that I can specify what % has been uploaded so far?
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Author Comment

ID: 2549587

Thanks, it worked.

One more thing: Is there absolutely no way of getting the total file size just as upload starts? So that I can specify what % has been uploaded so far?

Expert Comment

ID: 2549588
See my comment above.
LVL 16

Expert Comment

ID: 2550475

you are not totally accurate when you say "...what you get is actually the size *after* the file has already been uploaded".

you get the size of the file even as it is being read and not after the file has been uploaded. so if you want to abort the download after reaching a particular limit you can still do that and not have the entire file.

However, in this case i think leoleo would be better off using the solution you have provided.

Accepted Solution

alien_life_form earned 30 total points
ID: 2550581

Well, the way does uploads reads, in part:

$tmpfile = new TempFile;
$tmp = $tmpfile->as_string;

$filehandle = Fh->new($filename,$tmp,$PRIVATE_TEMPFILES);

$CGI::DefaultClass->binmode($filehandle) if $CGI::needs_binmode;
chmod 0600,$tmp;    # only the owner can tamper with it

my ($data);
local($\) = '';
while (defined($data = $buffer->read)) {
    print $filehandle $data;

here, $buffer is an instance of MultipartBuffer which deep inside is little more than a filehandle. I can see no good way to get into the while (but I'll be glad to be shown one), except by perhaps overriding the read method in  MultipartBuffer - which may be preferable than overriding the whole shebang, anyway.

Looks to me that, by the time that the sub returns, the upload is over. Now it would be nice to have the possibility to supply a callback function to oversee the process, but Lincoln (Stein) will have to take care of that... :-)

LVL 16

Expert Comment

ID: 2559384
leoleo, was your problem solved by the answers you got?

Pl. let  the forum know.

Author Comment

ID: 2560333

 I think so, I am still exploring the CGI module which I have not used much.

Thanks indeed.
LVL 16

Expert Comment

ID: 2561363
Glad to know that you have your solution :). Please go ahead & award thte points to the right answer


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