CURLOPT_HEADERDATA(3)      Library Functions Manual      CURLOPT_HEADERDATA(3)

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(3) or CURLOPT_HEADERFUNCTION(3) 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 win32 DLL, you MUST use a
       CURLOPT_WRITEFUNCTION(3) or CURLOPT_HEADERFUNCTION(3) if you set this
       option or you might experience crashes.

DEFAULT
       NULL

PROTOCOLS
       All

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
       Always

RETURN VALUE
       Returns CURLE_OK

SEE ALSO
       CURLOPT_HEADERFUNCTION(3), CURLOPT_WRITEFUNCTION(3),
       curl_easy_header(3)

libcurl                          April 26 2024           CURLOPT_HEADERDATA(3)