当dns为up和down时，curl apis不会更改值，但curl命令会提供成功/失败输出

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <iostream>
#include <sstream>
#include <fstream>
#include <errno.h>
#include <curl/curl.h>

using namespace std;



string gettimenow()
{
    time_t t = time(0);   // get time now
        struct tm * now = localtime( & t );
        std::ostringstream stm ;
        stm << (now->tm_year + 1900)<<"-"
             << (now->tm_mon + 1)<<"-"
             <<  now->tm_mday<<"-"
             << now->tm_hour<<"-"
             <<now->tm_min<<"-"
             <<now->tm_sec;
        return stm.str();
}


// proxyURL - https://web-proxy.ind.hp.com
//exampleURL - https://example.com
int main()
{
    string cmd = "curl -k  -x proxyURL:8080 -L exampleURL --connect-timeout 10";
    string output ="";
    string errorout = "";

    int i =0;
    while ( i< 50){
        cout<< "value i ="<<i<<endl;
        cout<<"sss 35 "<<gettimenow()<<endl;
    CURL *curl = curl_easy_init();
    if(curl) {
      CURLcode res;
      curl_easy_setopt(curl, CURLOPT_URL, "EXAMPLEURL");
      curl_easy_setopt(curl,CURLOPT_PROXY,"proxyURL");
      curl_easy_setopt(curl,CURLOPT_PROXYPORT,8080);
      curl_easy_setopt(curl,CURLOPT_PROXYTYPE,CURLPROXY_HTTP);
      curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, false);
      curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, false);
      curl_easy_setopt(curl, CURLOPT_TIMEOUT, 10L);
      res = curl_easy_perform(curl);
      curl_easy_cleanup(curl);
      if(res != CURLE_OK){
          cout<<"CURL failed with error ::"<<curl_easy_strerror(res)<<endl;
      }else
          cout<<"CURL api success "<<endl;
    }
    sleep(60);
    i++;
    }


    return 0;
}
#include <stdio.h>
#include <stdlib.h>
#include