inotify/demo_inotify.c

+/* demo_inotify.c
+
+   Demonstrate the use of the inotify API.
+
+   Usage: demo_inotify pathname...
+
+   The program monitors each of the files specified on the command line for all
+   possible file events.
+
+   This program is Linux-specific. The inotify API is available in Linux 2.6.13
+   and later.
+*/
 #include <sys/inotify.h>
 #include <limits.h>
 #include "tlpi_hdr.h"
 
 static void             /* Display information from inotify_event structure */
 displayInotifyEvent(struct inotify_event *i)
 {
     printf("    wd =%2d; ", i->wd);
     if (i->cookie > 0)
         printf("cookie =%4d; ", i->cookie);
 
     printf("mask = ");
     if (i->mask & IN_ACCESS)        printf("IN_ACCESS ");
     if (i->mask & IN_ATTRIB)        printf("IN_ATTRIB ");
     if (i->mask & IN_CLOSE_NOWRITE) printf("IN_CLOSE_NOWRITE ");
     if (i->mask & IN_CLOSE_WRITE)   printf("IN_CLOSE_WRITE ");
     if (i->mask & IN_CREATE)        printf("IN_CREATE ");
     if (i->mask & IN_DELETE)        printf("IN_DELETE ");
     if (i->mask & IN_DELETE_SELF)   printf("IN_DELETE_SELF ");
     if (i->mask & IN_IGNORED)       printf("IN_IGNORED ");
     if (i->mask & IN_ISDIR)         printf("IN_ISDIR ");
     if (i->mask & IN_MODIFY)        printf("IN_MODIFY ");
     if (i->mask & IN_MOVE_SELF)     printf("IN_MOVE_SELF ");
     if (i->mask & IN_MOVED_FROM)    printf("IN_MOVED_FROM ");
     if (i->mask & IN_MOVED_TO)      printf("IN_MOVED_TO ");
     if (i->mask & IN_OPEN)          printf("IN_OPEN ");
     if (i->mask & IN_Q_OVERFLOW)    printf("IN_Q_OVERFLOW ");
     if (i->mask & IN_UNMOUNT)       printf("IN_UNMOUNT ");
     printf("\n");
 
     if (i->len > 0)
         printf("        name = %s\n", i->name);
 }
 
 #define BUF_LEN (10 * (sizeof(struct inotify_event) + NAME_MAX + 1))
 
 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);
 }