Get a response into memory

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This example is a variation of the former that instead of sending the received data to stdout (which often is not what you want), this example instead stores the incoming data in a memory buffer that is enlarged as the incoming data grows.
It accomplishes this by using a write callback to receive the data.
This example uses a fixed URL string with a set URL scheme, but you can of course change this to use any other supported protocol and then get a resource from that instead.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
​
#include <curl/curl.h>
​
struct MemoryStruct {
  char *memory;
  size_t size;
};
​
static size_t
WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp)
{
  size_t realsize = size * nmemb;
  struct MemoryStruct *mem = (struct MemoryStruct *)userp;
​
  mem->memory = realloc(mem->memory, mem->size + realsize + 1);
  if(mem->memory == NULL) {
    /* out of memory */
    printf("not enough memory (realloc returned NULL)\n");
    return 0;
  }
​
  memcpy(&(mem->memory[mem->size]), contents, realsize);
  mem->size += realsize;
  mem->memory[mem->size] = 0;
​
  return realsize;
}
​
int main(void)
{
  CURL *curl_handle;
  CURLcode res;
​
  struct MemoryStruct chunk;
​
  chunk.memory = malloc(1);  /* will be grown as needed by the realloc above */
  chunk.size = 0;    /* no data at this point */
​
  curl_global_init(CURL_GLOBAL_ALL);
​
  /* init the curl session */
  curl_handle = curl_easy_init();
​
  /* specify URL to get */
  curl_easy_setopt(curl_handle, CURLOPT_URL, "https://www.example.com/");
​
  /* send all data to this function  */
  curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
​
  /* we pass our 'chunk' struct to the callback function */
  curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, (void *)&chunk);
​
  /* some servers do not like requests that are made without a user-agent
     field, so we provide one */
  curl_easy_setopt(curl_handle, CURLOPT_USERAGENT, "libcurl-agent/1.0");
​
  /* get it! */
  res = curl_easy_perform(curl_handle);
​
  /* check for errors */
  if(res != CURLE_OK) {
    fprintf(stderr, "curl_easy_perform() failed: %s\n",
            curl_easy_strerror(res));
  }
  else {
    /*
     * Now, our chunk.memory points to a memory block that is chunk.size
     * bytes big and contains the remote file.
     *
     * Do something nice with it!
     */
​
    printf("%lu bytes retrieved\n", (long)chunk.size);
  }
​
  /* cleanup curl stuff */
  curl_easy_cleanup(curl_handle);
​
  free(chunk.memory);
​
  /* we are done with libcurl, so clean it up */
  curl_global_cleanup();
​
  return 0;
}
Get a simple HTTP page
Submit a login form over HTTP
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