I have the following curl code, which make a request to website and retrieve data from it, it works well, but I want to store my data in a string and not in the output window. Any idea?

#include <stdio.h>
#include <curl/curl.h>

int main(void)
{
  CURL *curl;
  CURLcode res;

  curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "http://api.hostip.info/get_html.php?ip=xxx.xxx.xx.xxx");
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
    res = curl_easy_perform(curl);
    if(res != CURLE_OK)
      fprintf(stderr, "curl_easy_perform() failed: %s\n",
              curl_easy_strerror(res));
    curl_easy_cleanup(curl);
  }
  return 0;
}

int http_get_response(void *buffer, size_t size, size_t rxed, char **msg_in)
{
    char *c;

    if (asprintf(&c, "%s%.*s", *msg_in, size * rxed, buffer) == -1) {
        free(*msg_in);
        msg_in = NULL;
        return -1;
    }

    free(*msg_in);
    *msg_in = c;

    return size * rxed;
}

and add the following curl option in your main

char *msg_in = calloc(1,sizeof(char));

curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, http_get_response);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &msg_in);

Then you will get the message in the msg_in

EDIT

do not forget to free msg_in when it become uselless in your program

free(msg_in); msg_in = NULL;