/*
 This is a program from the book AP on page 194 to test vfork function,
According to the defination in the book, vfork will let child process run
in the same address space of parent space and parent process will not resume
until child process call an exec or exit;
Therefore, the result in the below sample should give result

   before vfork
   child glob = 11   var = 21
   parent glob = 11  var = 21

BUT the sample here seems giving diffrent result,

   before vfork
   parent glob = 10  var = 20
   child glob = 11   var = 21

WHY ??

*/

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>

int glob ;
int
main(void){
 int var;
 pid_t pid;

 glob = 10;
 var  = 20;
 printf("before vfork\n");

 if (vfork()== 0 ) {
   sleep(1);
   glob++;
   var++;
   printf("child glob= %d  var= %d\n", glob, var);
   exit(0); 
 } else {
  printf("parent glob= %d  var= %d\n", glob, var);

 }

}