// Sample signal() program (man signal) and (man sigaction)

// Creates two children process, both of which will print their PID and do some work

// The parent will just do some work and then send a signal to the children to kill
//    themselves (horrible isn't it?)




#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h> // NEW!!!

#define NCHILDS (2)

void signal_handler(int s)
{
	printf("Signal handler.\n");
	if (s == SIGUSR1)
	{
		printf("Child %d - signal SIGUSR1 raised.\n", getpid());

	}
	else if (s == SIGUSR2)
	{
		printf("Child %d - signal SIGUSR2 raise.\n", getpid());
		printf("killing child\n");
		exit(0);
	}

	fflush(NULL);

	return;
}


int main(int argc, char** argv)
{
	int childpid[NCHILDS];

	int i;
	int j;
	int fChild = 0; // flag if its a child proc or not

	struct sigaction sa;
	int p_pid, p_sig, p_sig2;

	printf("Sample fork() program.\n");


	printf("Parent's PID is %d\n", getpid());

	printf("Forking...\n");
	for (i = 0; i < NCHILDS; i++)
	{
		childpid[i] = fork();

		// Get out of the loop if it's a child process
		if (childpid[i] == 0)
		{
			fChild = 1;
			break;
		}
	}

	if (fChild == 1)
	{
		/* child proc */


		/* NEW - install a signal handler so the parent can use it */

		sa.sa_handler = signal_handler;
		sa.sa_flags = 0;

		// attach signal handler to the process
		//  when the signal SIGUSR1 is raised, we'll do something
		if (sigaction(SIGUSR1, &sa, NULL) == -1)
		{
			printf("Something broke.\n");
			return 0;
		}
		if (sigaction(SIGUSR2, &sa, NULL) == -1)
		{
			printf("Something broke.\n");
			return 0;
		}

		printf("Child born - PID = %d\n", getpid());

		for (j = 0; j < 100000000; j++)
		{
			//printf("Child %d goes to sleep.\n", getpid());
			//printf("Child %d wakes up.\n", getpid());
			rand();
			sleep(1);
		}
	}
	else
	{
		/* parent */
		sleep(2); // Make sure the childs are created first.

		printf("Parent's two children are %d %d\n", childpid[0], childpid[1]);

		do
		{
			printf("Enter a child's pid and a 1 or 2 (i.e. 220 1)\n");
			printf("Control-c to end.\n");
			scanf("%d %d", &p_pid, &p_sig);

			p_sig2 = (p_sig == 1) ? SIGUSR1 : SIGUSR2;
			if (kill(p_pid, p_sig2) == -1) // man kill -- sends the signal
			{
				printf("kill() didn't work.\n");
			}
		} while (1);

	}
	return 0;
}