SO #7

#include <signal.h>
#include <stdio.h>
#include <stdlib.h>

double old_val = 0;
double val = 0;
double r = 0;

int pos = 0;

int child_pid;

int counter = 0;

void child_end(int sig)
{
  printf("Child %d has ended. Exit code: %d\n", child_pid, sig);
  exit(0);
}

void print_value(int sig)
{
  printf("Value: %f\n", val);
  counter++;
  if(counter == 2)
  {
    exit(15);
  }
}

void child_proc() {
  struct sigaction sig;
  sig.sa_handler = print_value;
  sig.sa_flags = 0;
  sigaction(SIGUSR1, &sig, NULL);

  printf("Child process started.\n");


  while(1)
  {
    val = old_val + (1/r);
    old_val = val;
  }

}

void print_main(int sig)
{
  printf("ALARM\n");
  kill(child_pid,SIGUSR1);
  if(pos == 3) pos = 0;
  switch(pos)
  {
    case 0: {
      printf("****\n");
      break;
    }
    case 1: {
      printf("++++\n");
      break;
    }
    case 2: {
      printf("----\n");
      break;
    }
    default: break;
  }
  pos++;
}

void parent_proc()
{
  printf("Parent process started.\n");

  while(1)
  {
    //alarm outside of while
    alarm(1);
  }
}

int main(int argc, char *args[]) {
  struct sigaction sig;
  sig.sa_handler = child_end;
  sig.sa_flags = 0;
  sigemptyset (&sig.sa_mask);
  if(sigaction(SIGCHLD, &sig, NULL) < 0)
  {
    printf("Error setting handler for SIGCHLD.\n");
    exit(0);
  }

  struct sigaction mainsa;
  mainsa.sa_handler = print_main;
  mainsa.sa_flags = 0;
  sigemptyset (&mainsa.sa_mask);
  if(sigaction(SIGALRM, &mainsa, NULL) < 0)
  {
    printf("Error setting handler for SIGALRM.\n");
    exit(0);
  }

  if(argc != 3)
  {
    fprintf(stderr, "Usage: %s <a0> <r>\n", args[0]);
    exit(1);
  }

  old_val = atof(args[1]);
  r = atof(args[2]);

  if ((child_pid = fork()) < 0)
  {
    printf("Error creating child process\n");
    exit(1);
  }
  if (child_pid == 0)
  {
    child_proc();
    exit(0);
  } else
  {
    //signals here
    parent_proc();
  }
  exit(0);

}