A program that uses libcurl to fetch data in JSON format. Later parsed with json-c

curltest.c

/**
 * A demo of how to get data from a website in JSON format
 * I'll get data from this site:
 * http://jsonplaceholder.typicode.com/posts
 *
 * Requirements:
 *
 * json-c - https://github.com/json-c/json-c
 * libcurl - http://curl.haxx.se/libcurl/c
 *
 * Build:
 *
 * gcc curltest.c -lcurl -ljson-c -o curltest
 *
 * Run:
 *
 * ./curltest
 *
 */

/* standard includes */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* json-c (https://github.com/json-c/json-c) */
#include <json-c/json.h>

/* libcurl (http://curl.haxx.se/libcurl/c) */
#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()
{
        /* url to test site */
        char *url = "http://jsonplaceholder.typicode.com/posts/";

        CURL *curl_handle;
        CURLcode res;

        struct MemoryStruct chunk;
        chunk.memory = malloc(1);
        chunk.size = 0;

        curl_global_init(CURL_GLOBAL_ALL);
        curl_handle = curl_easy_init();
        curl_easy_setopt(curl_handle, CURLOPT_URL, url);
        curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
        curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, (void *)&chunk);
        curl_easy_setopt(curl_handle, CURLOPT_USERAGENT, "libcurl-agent/1.0");

        /* get it! */
        res = curl_easy_perform(curl_handle);
        //printf("%s", chunk.memory);

        /* check for errors */
        if(res != CURLE_OK) {
                fprintf(stderr, "curl_easy_perform() failed: %s\n",
                        curl_easy_strerror(res));
        }
        else {
                printf("%lu bytes retrieved\n", (long)chunk.size);
                char *mystring = chunk.memory;
                //  printf("%s", mystring);

                json_object *jobj = json_tokener_parse(mystring);
                printf("jobj from str:\n---\n%s\n---\n", json_object_to_json_string_ext(jobj, JSON_C_TO_STRING_SPACED | JSON_C_TO_STRING_PRETTY));
        }

        /* cleanup curl stuff */
        curl_easy_cleanup(curl_handle);

        free(chunk.memory);

        /* we're done with libcurl, so clean it up */
        curl_global_cleanup();

        return 0;
}