code:под-итог с примером

main.cpp

@@ -6,6 +6,7 @@
 #include "svg.hpp"
 #include <sstream>
 #include "curl.hpp"
+#include <string>
 
 using namespace std;
 
@@ -32,22 +33,47 @@ Input input_data(istream& in, bool prompt)
     return inp;
 }
 
-int main(int argc, char* argv[])
-{
-    if (argc > 1)
+size_t
+write_data(void* items, size_t item_size, size_t item_count, void* ctx) {
+    stringstream* buffer = reinterpret_cast<stringstream*>(ctx);
+    size_t data_size = item_size * item_count;
+    (*buffer).write(reinterpret_cast<const char*>(items), data_size);
+    return data_size;
+}
+
+Input
+download(const string& adress){
+    curl_global_init(CURL_GLOBAL_ALL);
+    stringstream buffer;
+    CURL* curl = curl_easy_init();
+    if(curl)
     {
-        CURL* curl = curl_easy_init();
-        if(curl)
+        CURLcode res;
+        curl_easy_setopt(curl, CURLOPT_URL, adress.c_str());
+        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
+        curl_easy_setopt(curl, CURLOPT_WRITEDATA, &buffer);
+        res = curl_easy_perform(curl);
+        if (res != CURLE_OK)
         {
-            CURLcode res;
-            curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
-            res = curl_easy_perform(curl);
-            curl_easy_cleanup(curl);
+            cerr << curl_easy_strerror(res);
+            exit(1);
         }
+        curl_easy_cleanup(curl);
     }
+    curl_global_cleanup();
+    return input_data(buffer, false);
+}
+
+int main(int argc, char* argv[])
+{
     curl_global_init(CURL_GLOBAL_ALL);
-    bool prompt = true;
-    auto in = input_data(cin, prompt);
+    
+    Input in;
+    if (argc > 1)
+        in = download(argv[1]);
+    else
+        in = input_data(cin, true);
+    
     auto bins = make_histogram(in.numbers, in.bin_count);
     show_histogram_svg(bins);
     return 0;