cURL / Mailing Lists / curl-library / Single Mail


Re: Doesn't fwrite() return the number of objects written, not the number of bytes?

From: Daniel Stenberg <>
Date: Fri, 31 Jul 2009 09:31:57 +0200 (CEST)

On Wed, 29 Jul 2009, Петър Иванов wrote:

> I was just writing a simple FTP-based application that needs to download
> files from an FTP server. I am passing a FILE pointer to my
> CURLOPT_WRITEFUNCTION. I return (size * fwrite(buffer, size, nmemb, stream)
> ). I do this because 'man fwrite' says that fwrite() returns nmemb in case
> successful. Is this correct? Does the write callback really needs to return
> the number of bytes processed? It may overflow, as the return value is also
> size_t. The FTP example here:
> returns fwrite() only.
> Or maybe I am missing something?

Well... :-)

You're right in principle but as libcurl will ALWAYS pass in size as '1' the
sum of 'size * nmemb' is in fact the number of bytes...

Someone worked on getting the examples updated to better reflect this in the
past, but I lost the patch and I'm not convinced it is very important to make
the examples more complicated to communicate that point properly.

Received on 2009-07-31