Writing the software

#include <stdio.h>
#include <libgen.h> // For basename()
#include <curl/curl.h>


/*
 * From http://stackoverflow.com/questions/7963170/how-to-do-remove-the-last-occurrence-of-a-string-from-another-string
*/
size_t write_data(void *ptr, size_t size, size_t nmemb, FILE *stream) {
    size_t written;
    written = fwrite(ptr, size, nmemb, stream);
    return written;
}


int main(int argc, char* args[]) {
    
    // Assume a single argument
    if (argc != 2) {
        printf("Please enter a URL");
        return 1;
    }

    // Declare a pointer to a CURL *easy* handle
    // http://curl.haxx.se/libcurl/c/curl_easy_init.html
    CURL *curl;
    
    // If there is any error, this is the variable in which it will be stored.
    // http://curl.haxx.se/libcurl/c/curl_easy_strerror.html
    CURLcode res;

    // This (file-handle) is what we'll use to write to disk
    FILE *fp;

    // Apparently, this function must be the first function call.
    // http://curl.haxx.se/libcurl/c/curl_easy_init.html
    curl = curl_easy_init();
    if(curl) {
        // We configure the `curl` struct to point
        // to the first argument we passed from the
        // terminal.
        curl_easy_setopt(curl, CURLOPT_URL, args[1]);
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);

        // Now that we've passed the full url, let's
        // get the last part of the URL, which will
        // become our file-name.
        char *output = basename(args[1]);
        fp = fopen(output, "wb");
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);

        // Perform the request, res will get the return code
        res = curl_easy_perform(curl);

        // Always cleanup
        curl_easy_cleanup(curl);
    }

    return 0;
}