Man page - curlopt_headerdata(3)

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Manual

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 Windows 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

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(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).