Introduction

RSS (Really Simple Syndication) is a standardized format used for delivering regularly updated content such as news, blogs, and podcasts. In this tutorial, we will create a simple RSS Feed Reader in the C programming language. Our objective is to fetch and display the contents of an RSS feed from a specified URL.

Objective

The goal is to design a basic RSS feed reader in C that fetches RSS data from an internet source, parses the XML data, and outputs the titles of the items included in the RSS feed. This will give an overview of how to work with URLs, XML data, and simple I/O operations in C.

Code

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

#define BUFFER_SIZE 4096

// Struct to store data received from the server
struct MemoryStruct {
    char *memory;
    size_t size;
};

// Callback function to write data to memory
size_t write_callback(void *ptr, size_t size, size_t nmemb, struct MemoryStruct *data) {
    size_t total_size = size * nmemb;
    data->memory = realloc(data->memory, data->size + total_size + 1);
    if (data->memory == NULL) {
        printf("Not enough memory (realloc failed).");
        return 0;
    }
    memcpy(&(data->memory[data->size]), ptr, total_size);
    data->size += total_size;
    data->memory[data->size] = 0;
    return total_size;
}

// Function to fetch RSS feed from URL
void fetch_rss_feed(const char *url) {
    CURL *curl;
    CURLcode res;
    struct MemoryStruct data;
    
    data.memory = malloc(1);
    data.size = 0;

    curl_global_init(CURL_GLOBAL_DEFAULT);
    curl = curl_easy_init();
    if (curl) {
        curl_easy_setopt(curl, CURLOPT_URL, url);
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_callback);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&data);
        
        res = curl_easy_perform(curl);
        if (res != CURLE_OK) {
            fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
        } else {
            // Print the raw data received (XML content)
            printf("Raw RSS feed content:\n%s\n", data.memory);
        }
        
        curl_easy_cleanup(curl);
    }

    free(data.memory);
    curl_global_cleanup();
}

// Main function
int main() {
    const char *rss_url = "https://example.com/rss"; // Change to a valid RSS feed URL
    fetch_rss_feed(rss_url);
    return 0;
}

Explanation of Program Structure

The program is divided into several parts:

• MemoryStruct: This structure is used to store the data we receive from the RSS feed.
• write_callback: This function handles writing data to memory, ensuring that the content of the RSS feed is correctly stored as it is received from the server.
• fetch_rss_feed: This function makes an HTTP request to the given RSS feed URL using the libcurl library, and it retrieves the raw XML data.
• main: The entry point where we define the RSS feed URL and call the fetch function.

How to Run the Program

1. Ensure you have the libcurl library installed on your system.
2. Copy the code into a new file named rss_reader.c.
3. Open a terminal and navigate to the directory containing the file.
4. Compile the code using the following command: gcc -o rss_reader rss_reader.c -lcurl
5. Run the compiled program with: ./rss_reader.
6. Change the rss_url variable to a valid RSS feed URL (e.g., https://example.com/rss).