The long parameter upload set to 1 tells the library to prepare for and
perform an upload. The CURLOPT_READDATA(3) and
CURLOPT_INFILESIZE(3) or CURLOPT_INFILESIZE_LARGE(3) options are
also interesting for uploads. If the protocol is HTTP, uploading means using
the PUT request unless you tell libcurl otherwise.
Using PUT with HTTP 1.1 implies the use of a "Expect: 100-continue" header.
You can disable this header with CURLOPT_HTTPHEADER(3) as usual.
If you use PUT to a HTTP 1.1 server, you can upload data without knowing the
size before starting the transfer if you use chunked encoding. You enable this
by adding a header like "Transfer-Encoding: chunked" with
CURLOPT_HTTPHEADER(3). With HTTP 1.0 or without chunked transfer, you
must specify the size.
CURL *curl = curl_easy_init();
/* we want to use our own read function */
curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_callback);
/* enable uploading */
curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
/* specify target */
curl_easy_setopt(curl, CURLOPT_URL, "ftp://example.com/dir/to/newfile");
/* now specify which pointer to pass to our callback */
curl_easy_setopt(curl, CURLOPT_READDATA, hd_src);
/* Set the size of the file to upload */
curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE, (curl_off_t)fsize);
/* Now run off and do what youve been told! */