/*for printf(), perror()*/
#include <stdio.h>
/*for putenv()*/
#include <stdlib.h>
/*for fork(), sleep()*/
#include <unistd.h>
/*for wait()*/
#include <sys/types.h>
#include <sys/wait.h>

extern char **environ;
int child_stat;

void print_env (header)
   char *header;
{
   int i;

   printf ("-= \%s =-\n", header);
   for (i = 0; environ[i] != NULL; i++)
       printf("\%s\n", environ[i]);
}
int main (argc, argv, env)
   int argc;
   char **argv;
   char **env;
{
   print_env ("Father, before environ changes");

   /*Let's born a child*/
   switch (fork ())
   {
       case 0: /*Child*/
           sleep (2); /*Child's and father's output do not overlap*/
           print_env("Child, after father's environ changes");
           break;

       case -1: /*Error*/
           perror ("Could not fork()");
           break;

       default: /*Father*/
           putenv ("LAMER=TEST"); /* It changes "environ", but not "env"*/
           print_env ("Father, after environ changes");
           wait (&child_stat); /*Wait for child to terminate*/
           break;
   }
   return 0;
}