Get a response into memory

This example is a variation of the former that instead of sending the receiveddata to stdout (which often is not what you want), this example instead storesthe incoming data in a memory buffer that is enlarged as the incoming datagrows.

It accomplishes this by using awrite callback toreceive the data.

This example uses a fixed URL string with a set URL scheme, but you can ofcourse change this to use any other supported protocol and then get a resourcefrom that instead.

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <curl/curl.h>struct MemoryStruct {  char *memory;  size_t size;};static size_tmem_cb(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);  /* 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, mem_cb);  /* 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;}