[curl] Download URL to file

cURL provides two kinds of interface to access the internet: easy and multi. Easy interface is synchronous and efficient. The multi interface has asynchronous method also multi-file data transfer ability.

In this tutorial, we are going to demonstrate how to simply download an HTTP file from internet with cURL easy method in C++.

Easy interface

Let’s talk about the easy interface, steps for data transfer purpose can be separated into three.

curl_easy_init()

Initialization an easy-session and get a handle. The handle will be used as an input for the following functions.

curl_easy_setopt()

Setting all the options you want for the internet data transfer including URL, port or the way to write data.

curl_easy_perform()

After the options you want for the upcoming transfer has been settled. you can call the curl_easy_perform() function. It will do the entire job and won’t return until the job has been done or failed.

curl_easy_cleanup()

After the job has been done, the curl_easy_leanup() method will clean up the easy-session handle for you.

Here is a short demonstration of file downloading from http://www.example.com. We are going to save it to example.html in your local folder.

#include <stdio.h>
#include <curl/curl.h>
int main(void)
{
    CURL *curl;
    FILE *fp;
    CURLcode res;
    char *url = "http://www.example.com";
    char outfilename[FILENAME] = "example.html";
    curl = curl_easy_init();
    if (curl)
    {
        fp = fopen(outfilename,"wb");
        curl_easy_setopt(curl, CURLOPT_URL, url);
        curl_easy_setopt(curl,CURLOPT_WRITEFUNCTION, NULL);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
        res = curl_easy_perform(curl);
        curl_easy_cleanup(curl);
        fclose(fp);
    }
    return 0;
}

Options of curl_easy_setopt() are listed below:

Network Options	Function
CURLOPT_URL	URL to work on
CURLOPT_WRITEFUNCTION	Callback for writing data
CURLOPT_WRITEDATA	Data pointer to pass to the write callback

Successful run will give you the ability to download the html file you want like this :-D

keywords: cURL, C++, Code::Block