使用curl下载文件

curl是一个非常好的网络传输库，使用也很简单。常用的使用方式是用它来下载资源文件，以下提供一个下载方法

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

 using namespace std;

 int download(string url, string local_file, int down_speed)
 {
   CURL *image;
   CURLcode imgresult;
   FILE *fp;
   //url_download.c_str();

     image = curl_easy_init();
     if( image )
      {
         //Open File
         fp = fopen(local_file.c_str(), "w");
         if( fp == NULL ) cout << "File cannot be opened";

         curl_easy_setopt(image, CURLOPT_WRITEFUNCTION, NULL);
         curl_easy_setopt(image, CURLOPT_WRITEDATA, fp);
         curl_easy_setopt(image, CURLOPT_URL, url.c_str());
         curl_easy_setopt(image, CURLOPT_FOLLOWLOCATION, );
 //这里限速 100KB/s
         curl_easy_setopt(image, CURLOPT_MAX_RECV_SPEED_LARGE, (curl_off_t) * );
         curl_easy_setopt(image, CURLOPT_NOPROGRESS, );
         //CURLOPT_RESUME_FROM

         // Grab image
         imgresult = curl_easy_perform(image);
         if( imgresult )
             {
                 cout << "Cannot grab the File!\n";
             }
     }
     //Clean up the resources
     curl_easy_cleanup(image);
     //Close the file
     fclose(fp);
     return ;
 }