Introduction

In this guide, we will learn how to track and display stock prices using an API in C programming. By leveraging stock market APIs, you can retrieve real-time stock data, such as the current price of a stock, its opening price, and more. We will focus on using a stock price API that allows fetching data in real time.

Objective

The goal of this program is to:

• Retrieve real-time stock price data from an API.
• Parse and display the relevant stock information on the screen.
• Use a simple and effective C program to fetch and show stock prices.

Code

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

#define API_KEY "your_api_key"  // Replace with your API key
#define STOCK_SYMBOL "AAPL"    // Replace with the desired stock symbol

// Function to write the response data into a string
size_t WriteCallback(void *contents, size_t size, size_t nmemb, void *userp) {
    size_t total_size = size * nmemb;
    strncat(userp, contents, total_size);
    return total_size;
}

void get_stock_price(const char *symbol) {
    CURL *curl;
    CURLcode res;
    char url[256];
    char response[1024] = "";  // Buffer to store the response

    // Construct the URL with the stock symbol and API key
    snprintf(url, sizeof(url), "https://api.example.com/stock/%s?apikey=%s", symbol, API_KEY);
    
    // Initialize CURL
    curl_global_init(CURL_GLOBAL_DEFAULT);
    curl = curl_easy_init();

    if (curl) {
        // Set the URL for the request
        curl_easy_setopt(curl, CURLOPT_URL, url);

        // Set the function to write the response
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteCallback);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, response);

        // Perform the request
        res = curl_easy_perform(curl);

        if (res != CURLE_OK) {
            fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
        } else {
            printf("Stock Data: %s\n", response); // Display the response
        }

        // Clean up
        curl_easy_cleanup(curl);
    }

    curl_global_cleanup();
}

int main() {
    printf("Fetching stock price for symbol: %s\n", STOCK_SYMBOL);
    get_stock_price(STOCK_SYMBOL);
    return 0;
}
        

Explanation

This C program fetches the stock price of a specified symbol using a stock market API. Here’s an overview of the main components:

• API_KEY: Replace this with your actual API key from the stock market provider.
• STOCK_SYMBOL: The stock symbol for which you want to track the price (e.g., AAPL for Apple).
• WriteCallback function: This function is used to store the API response into a string, which will later be processed or displayed.
• get_stock_price function: This function constructs the API URL, initializes the CURL library, performs the API call, and prints the response to the screen.
• curl_easy_setopt and curl_easy_perform: These are the key CURL functions that set options and perform the HTTP request.

How to Run the Program

1. Install CURL library on your system (if not already installed).
2. Replace the API_KEY with a valid key from the API provider (such as Alpha Vantage, Yahoo Finance, etc.).
3. Set the desired stock symbol in STOCK_SYMBOL.
4. Compile the C program using a C compiler, e.g., gcc stock_tracker.c -o stock_tracker -lcurl.
5. Run the program using ./stock_tracker in your terminal.
6. The program will output the stock data in the console, depending on the response format from the API.