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CURLOPT_HEADERDATA(3)               libcurl              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 will be passed in to the respective callback.

       If neither of those options are set, pointer must be a valid FILE * and
       it will be 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 will 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 = (struct my_info *)userdata;

         /* now this callback can access the my_info struct */

         return nitems * size;
       }

       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),

ibcurl 8.1.2                    April 26, 2023           CURLOPT_HEADERDATA(3)