CURLOPT_POSTFIELDSIZE - Man Page

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_POSTFIELDSIZE, long size);

Set the size of the data buffer to POST to prevent libcurl from doing a strlen() to figure out the data size. When this option is used you can post fully binary data, which otherwise is likely to fail. If this size is set to -1, libcurl uses strlen() to get the size or relies on the CURLOPT_READFUNCTION(3) (if used) to signal the end of data.

You must make sure that the set size is not larger than the provided buffer.

If you post more than 2GB, use CURLOPT_POSTFIELDSIZE_LARGE(3).

-1

This functionality affects http, mqtt and rtsp

#include <string.h> /* for strlen */

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    static const char *data = "data to send";

    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

    /* size of the POST data */
    curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, (long)strlen(data));

    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data);

    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

Added in curl 7.2

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).

CURLOPT_POSTFIELDS(3), CURLOPT_POSTFIELDSIZE_LARGE(3)