// SPDX-License-Identifier: GPL-2.0
#define _GNU_SOURCE     /* needed to get the defines */
#include <fcntl.h>      /* in glibc 2.2 this has the needed
                                   values defined */
#include <signal.h>
#include <stdio.h>
#include <unistd.h>

static volatile int event_fd;

static void handler(int sig, siginfo_t *si, void *data)
{
        event_fd = si->si_fd;
}

int main(void)
{
        struct sigaction act;
        int fd;

        act.sa_sigaction = handler;
        sigemptyset(&act.sa_mask);
        act.sa_flags = SA_SIGINFO;
        sigaction(SIGRTMIN + 1, &act, NULL);

        fd = open(".", O_RDONLY);
        fcntl(fd, F_SETSIG, SIGRTMIN + 1);
        fcntl(fd, F_NOTIFY, DN_MODIFY|DN_CREATE|DN_MULTISHOT);
        /* we will now be notified if any of the files
           in "." is modified or new files are created */
        while (1) {
                pause();
                printf("Got event on fd=%d\n", event_fd);
        }
}