/* File:  ~liux/public_html/courses/cop4610/examples/simple-env.cc
   Purpose: Demonstrate how to use list all environmental variables
            for COP4610
   Author:  Xiuwen Liu, based on an example in Advanced Programming
            in the UNIX Environment, by W. Richard Stevens, 
            Addison-Wesley, 1992
   On the web: 
     http://www.cs.fsu.edu/~liux/courses/cop4610/examples/simple-env.cc
   Compiling command:
     g++ -o simple-env simple-env.cc
*/

#include <sys/types.h>
#include <strings.h>
#include <sys/wait.h>
#include <signal.h>
#include <stdio.h>
#include <unistd.h>
#include <iostream.h>
#include <stdlib.h>

extern char **environ;
int   interrupted;
int main(int argc, char *argv[], char *envp[])
{
  int i;
  char env_name[256];
  char env_value[256];
  char env_str[256];
  
  cout << "There are two ways to show environmental variables.\n";
  cout << "First through external variable \"environ\"\n";

  cout << "Name for a new environment variable: ";
  cin.getline((char *)env_name, (int)256);
  cin.clear();
  cout << "Value for the new environment variable: ";
  cin.getline((char *)env_value, (int)256);
  sprintf(env_str,"%s=%s", env_name, env_value);
  if (putenv(env_str) < 0) {
    perror("putenv");
  }
  cout << endl;
  i = 0;
  while(environ[i] != NULL) {
    cout << "environ " << i << " -> " << environ[i] << endl;
    i++;
  }

  cout << "Second way through the third argument of main \"envp\"\n";  
  i =0;
  while(envp[i] != NULL) {
    cout << "envp " << i << " -> " << envp[i] << endl;
    i++;
  }
  
  execlp("env","env", (char *)NULL);  
  
  return 0;
}