CURLOPT_HEADERDATA explained

Name

CURLOPT_HEADERDATA - pointer to pass to header callback

Synopsis

#include <curl/curl.h>
 
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HEADERDATA, void *pointer);

Description

Pass a pointer to be used to write the header part of the received data to.

If CURLOPT_WRITEFUNCTION or CURLOPT_HEADERFUNCTION is used, pointer is passed in to the respective callback.

If neither of those options are set, pointer must be a valid FILE * and it is used by a plain fwrite() to write headers to.

If you are using libcurl as a Windows DLL, you MUST use a CURLOPT_WRITEFUNCTION or CURLOPT_HEADERFUNCTION if you set this option or you might experience crashes.

Default

NULL

Protocols

This functionality affects all supported protocols

Example

struct my_info {
  int shoesize;
  char *secret;
};
 
static size_t header_callback(char *buffer, size_t size,
                              size_t nitems, void *userdata)
{
  struct my_info *i = userdata;
  printf("shoe size: %d\n", i->shoesize);
  /* now this callback can access the my_info struct */
 
  return nitems * size;
}
 
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    struct my_info my = { 10, "the cookies are in the cupboard" };
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
 
    curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, header_callback);
 
    /* pass in custom data to the callback */
    curl_easy_setopt(curl, CURLOPT_HEADERDATA, &my);
 
    curl_easy_perform(curl);
  }
}

Availability

Added in curl 7.10

Return value

curl_easy_setopt returns a CURLcode indicating success or error.

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