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

#define SIGRT0 (SIGRTMIN + 3)
#define SIGRT1 (SIGRTMIN + 2)
#define SIGRT2 (SIGRTMIN + 1)
#define SIGRT3 (SIGRTMIN + 0)

void handler(int signum, siginfo_t *info, void *unused) {
    if (signum == SIGRT0) printf("Rcv sig RT0\n");
    else if (signum == SIGRT1) printf("Rcv sig RT1\n");
    else if (signum == SIGRT2) printf("Rcv sig RT2\n");
    else if (signum == SIGRT3) printf("Rcv sig RT3\n");
    else printf("Rcv sig Unknow\n");
}

int main(int argc, char *argv[]) {
    struct sigaction descriptor;
    descriptor.sa_flags = SA_SIGINFO;
    descriptor.sa_sigaction = handler;
    sigfillset(&(descriptor.sa_mask));

    sigaction(SIGRT0, &descriptor, NULL);
    sigdelset(&(descriptor.sa_mask), SIGRT0);
    sigaction(SIGRT1, &descriptor, NULL);
    sigdelset(&(descriptor.sa_mask), SIGRT1);
    sigaction(SIGRT2, &descriptor, NULL);
    sigdelset(&(descriptor.sa_mask), SIGRT2);
    sigaction(SIGRT3, &descriptor, NULL);

    pid_t childPid = fork();
    if (childPid == 0) {
        // child
        struct timespec request = {2, 0}, remaining;
        clock_nanosleep(CLOCK_MONOTONIC, 0,&request, &remaining);
    } else {
        // parent
        union sigval envelope;

        struct timespec request = {1, 0}, remaining;
        clock_nanosleep(CLOCK_MONOTONIC, 0,&request, &remaining);

        sigqueue(childPid, SIGRT0, envelope);
        sigqueue(childPid, SIGRT1, envelope);
        sigqueue(childPid, SIGRT2, envelope);
        sigqueue(childPid, SIGRT3, envelope);

        clock_nanosleep(CLOCK_MONOTONIC, 0,&request, &remaining);
    }
    exit(EXIT_SUCCESS);
}