#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/shm.h>
#include <sys/ipc.h>
#include <sys/types.h>
#include <string.h>

struct memcon {
	int	length;
	char	stringa[1000];
};

struct memcon  	*pippo;

void sig_usr(int signo)
{
	if(signo == SIGUSR1)
		printf("\n Lunghezza = %d, stringa = %s \n",pippo->length, pippo->stringa );
	exit(0);
}

void sig_usr2(int signo)
{
	if(signo == SIGUSR1)
		printf("\n SIGUSR1 \n");
	else if(signo == SIGUSR2)
			printf("\n SIGUSR2 \n");
	else
		printf("\n segnale = %d\n", signo);
}

int main(int argc, char *argv[])
{
	int shm_id, pid, pos=0;


	signal(SIGUSR1, sig_usr);
	signal(SIGUSR2, sig_usr2);

	shm_id = shmget(IPC_PRIVATE, sizeof(struct memcon), 0666);
	pippo = shmat(shm_id, 0, 0); 
	pippo->length = 0;	
	
	sprintf(pippo->stringa + pippo->length, "%s", argv[1]);
	pippo->length += strlen(argv[1]);
	printf("\n gli ultimi 4 char scritti in memoria condivisa: %s\n", pippo->stringa + pippo->length-4);
//	sprintf(pippo->stringa + pippo->length, "pong");
//	pippo->length +=4;

	while(1)
	{
		pid = fork();
		if(pid == 0)
		{
			if(strncmp(pippo->stringa+pippo->length-4, "ping", 4) == 0)	
				sprintf(pippo->stringa + pippo->length, "pong");
			else
				sprintf(pippo->stringa + pippo->length, "ping");
			pippo->length +=4;
			if(pippo->length > 20)
				kill(getppid(), SIGUSR1);
			exit(0);
		}
		waitpid(pid,NULL,0);
	}

}