gistfile1.txt

#include <signal.h>
#include <time.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/syscall.h>
#include <pthread.h>

void *thr(void *arg) {
			struct sigevent sev = {};
			sev.sigev_notify = SIGEV_THREAD;
			sev.sigev_signo = SIGURG;
			timer_t timerid;
			if (syscall(SYS_timer_create, CLOCK_REALTIME, &sev, &timerid))
				exit(printf("timer_create: %d\n", errno));
			itimerspec new_value;
			new_value.it_interval.tv_sec = 0;
			new_value.it_interval.tv_nsec = 0;
			new_value.it_value.tv_sec = 0;
			new_value.it_value.tv_nsec = 500;
			if (syscall(SYS_timer_settime, timerid, TIMER_ABSTIME, &new_value, NULL))
				exit(printf("timer_settime: %d\n", errno));
			exit(1);
			return 0;
}

int main() {
	int fd[2];
	if (pipe(&fd[0]))
		exit(printf("pipe failed: %d\n", errno));
	int pid = fork();
	if (pid < 0)
		exit(printf("fork failed: %d\n", errno));
	if (pid == 0) {
		int pid2 = fork();
		if (pid2 < 0)
			exit(printf("fork failed: %d\n", errno));
		if (pid2 == 0) {
			pthread_t th;
			pthread_create(&th, 0, thr, 0);
			for (;;)
				sleep(1);
		}
		for (;;)
			sleep(1);
	}
	close(fd[1]);
	usleep(100000);
	kill(pid, SIGKILL);
	char tmp;
	int n = read(fd[0], &tmp, 1);
	printf("read=%d/%d\n", n, errno);
	return 0;
}