/**
 * File: kill-puzzle.c
 * -------------------
 * Small program designed to illustrate how the kill routine
 * works.
 */

#include <stdbool.h>    // for bool
#include <unistd.h>     // for fork
#include <stdio.h>      // for printf
#include <sys/wait.h>   // for waitpid
#include <signal.h>     // for signal, kill

static pid_t pid;
static int counter = 0;

static void parentHandler(int unused) {
  counter++;
  printf("counter = %d\n", counter);
  kill(pid, SIGUSR1);
}

static void childHandler(int unused) {
  counter += 3;
  printf("counter = %d\n", counter);
}

int main(int argc, char *argv[]) {
  signal(SIGUSR1, parentHandler);
  if ((pid = fork()) == 0) {
    signal(SIGUSR1, childHandler);
    kill(getppid(), SIGUSR1);
    return 0;
  }
  
  waitpid(pid, NULL, 0);
  counter += 7;
  printf("counter = %d\n", counter);
  return 0;
}