#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <stdio.h>
#include <time.h>
#include <stdlib.h>

void parent_work();
void child_work();

int main(int argc, char *argv[])
{
  int pid;
  int start = 0;
  srand(time(NULL));         // initialize random number generator

  pid = fork();
  if (pid > 0)               // Parent case
  {
    parent_work();
    wait(NULL);              // Print before shell prompt appears
    printf("After call to wait() in parent\n");
  }
  else if (pid == 0)         // Child case
    child_work();
  else                       // If unable to fork a process
    exit(1);
  printf("\n");
}

void parent_work()
{
  int i, j;
  int r = rand() % 10;                      // Decide how much "work" to do

  for (i = 0; i < 10; ++i)
  {
    for (j = 0; j < 7000000 * r; ++j)       // Do the "work"
      ;
    printf("i = %d, Parent\n", i);
  }
}

void child_work()
{
  int i, j;
  int r = rand() % 10;                      // Decide how much "work" to do

  for (i = 0; i < 10; ++i)
  {
    for (j = 0; j < 10000000 * r; ++j)       // Do the "work"
      ;
    printf("i = %d, Child\n", i);
  }
}

/* Example output:
i = 0, Parent
i = 0, Child
i = 1, Parent
i = 1, Child
i = 2, Parent
i = 3, Parent
i = 2, Child
i = 4, Parent
i = 3, Child
i = 5, Parent
i = 6, Parent
i = 4, Child
i = 7, Parent
i = 5, Child
i = 8, Parent
i = 9, Parent
i = 6, Child
i = 7, Child
i = 8, Child
i = 9, Child

After call to wait() in parent
*/