kqueue/kqtimer.c

   1 /* compile with:
   2    gcc kqtimer.c -o kqtimer -Wall -W -Wextra -ansi -pedantic */
   3
   4 #include <sys/event.h>
   5 #include <sys/time.h>
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <string.h>   /* for strerror() */
   9 #include <unistd.h>
  10
  11 /* function prototypes */
  12 void diep(const char *s);
  13
  14 int main(void)
  15 {
  16     struct kevent change;    /* event we want to monitor */
  17     struct kevent event;     /* event that was triggered */
  18     pid_t pid;
  19     int kq, nev;
  20
  21     /* create a new kernel event queue */
  22     if ((kq = kqueue()) == -1)
  23         diep("kqueue()");
  24
  25     /* initalise kevent structure */
  26     EV_SET(&change, 1, EVFILT_TIMER, EV_ADD | EV_ENABLE, 0, 5000, 0);
  27
  28     /* loop forever */
  29     for (;;) {
  30         nev = kevent(kq, &change, 1, &event, 1, NULL);
  31
  32         if (nev < 0)
  33             diep("kevent()");
  34
  35         else if (nev > 0) {
  36             if (event.flags & EV_ERROR) {   /* report any error */
  37                 fprintf(stderr, "EV_ERROR: %s\n", strerror(event.data));
  38                 exit(EXIT_FAILURE);
  39             }
  40
  41             if ((pid = fork()) < 0)         /* fork error */
  42                 diep("fork()");
  43
  44             else if (pid == 0)              /* child */
  45                 if (execlp("date", "date", (char *)0) < 0)
  46                     diep("execlp()");
  47         }
  48     }
  49
  50     close(kq);
  51     return EXIT_SUCCESS;
  52 }
  53
  54 void diep(const char *s)
  55 {
  56     perror(s);
  57     exit(EXIT_FAILURE);
  58 }