gistfile1.c

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

int count = 0;
int pidMain;
int numThreads = 3;
int pids[3];
struct sigaction action;

void sigterm()
{
	printf("%d finished work\n", getpid());
	exit(0);
}

void father(int signo, siginfo_t *info, void *extra) 
{
	int i;
	void *ptr_val = info->si_value.sival_ptr;
	int int_val = info->si_value.sival_int;
	printf("Signal %d, value %d  \n", signo, int_val);
	count++;
	printf("father received signal, count = %d\n", count);
	if (count < 3)
		pause();
	if (count == 3)
		for (i = 0; i < numThreads; i++)
			kill(pids[i],SIGTERM);
}

void son(int SIG_NUM) 
{
	union sigval value;
	printf("son %d received signal\n", getpid() - pidMain);
	sleep(1);
	value.sival_int = getpid() - pidMain;
	sigqueue(pidMain,SIGUSR1, value);
	signal(SIGTERM, sigterm);
	pause();
}



int main(int argc, char *argv[]) {
    int i; 
	
	action.sa_flags = SA_SIGINFO; 
	action.sa_sigaction = &father;
	
    pidMain = getpid();
    
    for (i = 0; i < numThreads; i++)
    {
        pids[i] = fork();
        
        switch (pids[i]) {
            case 0:
                i = numThreads;
                printf("Proc %d created\n", getpid());
                signal(SIGUSR2, son);
                pause();
                break;
                
            case -1:
                perror("Creating process failed\n");
                exit(EXIT_FAILURE);
                break;
            
            default: ;  
        }
    }
    
    if (getpid() == pidMain) {
        sleep(1);
        printf("Starting first cycle %d\n", getpid());
        
        if (sigaction(SIGUSR1, &action, NULL) == -1) 
		{ 
			perror("sigusr: sigaction");
			_exit(1);
		}

        for (i = 0; i < numThreads; i++) 
		{
			printf("pids[i] = %d started\n", pids[i]);
			kill(pids[i], SIGUSR2);
        }
        pause();
        printf("Finishing first cycle %d\n", getpid());

    }
    
    printf("pid %d finished work\n", getpid());
        
    return (EXIT_SUCCESS);
}