#include <cstdlib.>
#include <iostream>
//#include <unistd.h>

using namespace std;
int main()
{
	//Display a particular env var
 char* descr = getenv("USERNAME");
 if (descr)
     cout<<"value of USERNAME is: "<< descr<<endl;
 else 
     cout<<"variable not defined"<<endl;

 //set an environ var
int stat = putenv("MYVAR=mystring");
if (!stat) {
   cout<<"failed to define environment variable"<<endl; 
}

 //display all environ vars
 for (int n=0; environ[n]; n++)
     cout << environ[n]<<endl;

 system("dir");

 system("set myvar2=mystring2");

 return 0;
}