poll.c

/* demo_inotify.c
+
+   Demonstrate the use of the poll API.
+
+   Usage: demo_inotify pathname...
+
+   The program monitors each of the files specified on the command line for all
+   possible file events.
+
+*/
 // #include <sys/inotify.h>
 #include <poll.h>
 #include <limits.h>
 #include "tlpi_hdr.h"
 
 static void             /* Display information from inotify_event structure */
 displayPollEvent(struct pollfd *p)
 {
	 short int evp;
     printf("    fd =%2d; ", p->fd);
 
     printf(" events = ");
     evp = p->events;
     if (evp & POLLIN)        printf("POLLIN "); /* There is data to read.  */
     if (evp & POLLPRI)       printf("POLLPRI ");/* There is urgent data to read.  */
     if (evp & POLLOUT)       printf("POLLOUT ");/* Writing now will not block.  */
     if (evp & POLLRDNORM)    printf("POLLRDNORM ");/* Normal data may be read.  */
     if (evp & POLLRDBAND)    printf("POLLRDBAND ");/* Priority data may be read.  */
     if (evp & POLLWRNORM)    printf("POLLWRNORM ");/* Writing now will not block.  */
     if (evp & POLLWRBAND)    printf("POLLWRBAND ");/* Priority data may be written.  */
     if (evp & POLLERR)       printf("POLLERR ");/* Error condition.  */
     if (evp & POLLHUP)       printf("POLLHUP ");/* Hung up.  */
     if (evp & POLLNVAL)      printf("POLLNVAL ");/* Invalid polling request.  */

/* These are extensions for Linux.  */
/*
# define POLLMSG        0x400
# define POLLREMOVE     0x1000
# define POLLRDHUP      0x2000
*/

     printf("\n");
 
 }
 
 #define BUF_LEN (10 * (sizeof(struct pollfd) + NAME_MAX + 1))
 
 #define usageErr(a,b)  printf(a,b),exit(1)
 #define errExit(a)   printf(a),exit(1)
 #define fatal errExit
 
 int
 main(int argc, char *argv[])
 {
     int inotifyFd, wd, j;
     char buf[BUF_LEN] __attribute__ ((aligned(8)));
     ssize_t numRead;
     char *p;
     struct inotify_event *event;
 
     if (argc < 2 || strcmp(argv[1], "--help") == 0)
         usageErr("%s pathname...\n", argv[0]);
 
     inotifyFd = inotify_init();                 /* Create inotify instance */
     if (inotifyFd == -1)
         errExit("inotify_init");
 
    /* For each command-line argument, add a watch for all events */

     for (j = 1; j < argc; j++) {
         wd = inotify_add_watch(inotifyFd, argv[j], IN_ALL_EVENTS);
         if (wd == -1)
             errExit("inotify_add_watch");
 
         printf("Watching %s using wd %d\n", argv[j], wd);
     }
 
     for (;;) {                                  /* Read events forever */
         numRead = read(inotifyFd, buf, BUF_LEN);
         if (numRead == 0)
             fatal("read() from inotify fd returned 0!");
 
         if (numRead == -1)
             errExit("read");
 
         printf("Read %ld bytes from inotify fd\n", (long) numRead);
 
         /* Process all of the events in buffer returned by read() */
 
         for (p = buf; p < buf + numRead; ) {
             event = (struct inotify_event *) p;
             displayInotifyEvent(event);
 
             p += sizeof(struct inotify_event) + event->len;
         }
     }
 
     exit(EXIT_SUCCESS);
 }