#include <iostream>

#include <string.h>

using namespace std;

extern char **environ;

void PrintValue(string value);

int main() {

     string name{"SILLY"};

     cout << endl;
     string  sillyVar{"SILLY=Now I am"};
     cout << "\tusing string sillyvar " << endl;

     cout << endl;

     PrintValue("LOGNAME");
     PrintValue(name);


     cout << "The environ pointer is " << environ << endl;

     if (putenv(const_cast<char *>(sillyVar.c_str())) == -1) {
         cerr << "Unable to change the SILLY environment variable" << endl;
     } else {

          PrintValue(name);
     }
     cout << "The environ pointer is " << environ << endl;

     cout << endl;
     cout << "Changing the value of sillyVar, DO NOT DO  THIS" << endl;
     sillyVar = "SILLY=No WAY!!";
     PrintValue(name);

     cout << "Removing " << name << endl;
     if(-1 == unsetenv(name.c_str())){
         cerr << "Unable to remove " << name << endl;
     }
     PrintValue(name);

     return 0;
}

void PrintValue(string name) {
     char * tmp;

     cout << endl;
     cout << "Searching for " << name << endl;
     cout << "\t";

     tmp = getenv(name.c_str());
      
     if (tmp != nullptr) {
        cout << name << " is " << tmp << endl;
     } else {
        cout << name << " is not in the environment. "<< endl;
     }

     cout << endl;
     
     return;
}