1INOTIFY(7) Linux Programmer's Manual INOTIFY(7)
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6 inotify - monitoring filesystem events
7
9 The inotify API provides a mechanism for monitoring filesystem events.
10 Inotify can be used to monitor individual files, or to monitor directo‐
11 ries. When a directory is monitored, inotify will return events for
12 the directory itself, and for files inside the directory.
13
14 The following system calls are used with this API:
15
16 * inotify_init(2) creates an inotify instance and returns a file
17 descriptor referring to the inotify instance. The more recent ino‐
18 tify_init1(2) is like inotify_init(2), but has a flags argument that
19 provides access to some extra functionality.
20
21 * inotify_add_watch(2) manipulates the "watch list" associated with an
22 inotify instance. Each item ("watch") in the watch list specifies
23 the pathname of a file or directory, along with some set of events
24 that the kernel should monitor for the file referred to by that
25 pathname. inotify_add_watch(2) either creates a new watch item, or
26 modifies an existing watch. Each watch has a unique "watch descrip‐
27 tor", an integer returned by inotify_add_watch(2) when the watch is
28 created.
29
30 * When events occur for monitored files and directories, those events
31 are made available to the application as structured data that can be
32 read from the inotify file descriptor using read(2) (see below).
33
34 * inotify_rm_watch(2) removes an item from an inotify watch list.
35
36 * When all file descriptors referring to an inotify instance have been
37 closed (using close(2)), the underlying object and its resources are
38 freed for reuse by the kernel; all associated watches are automati‐
39 cally freed.
40
41 With careful programming, an application can use inotify to efficiently
42 monitor and cache the state of a set of filesystem objects. However,
43 robust applications should allow for the fact that bugs in the monitor‐
44 ing logic or races of the kind described below may leave the cache
45 inconsistent with the filesystem state. It is probably wise to do some
46 consistency checking, and rebuild the cache when inconsistencies are
47 detected.
48
49 Reading events from an inotify file descriptor
50 To determine what events have occurred, an application read(2)s from
51 the inotify file descriptor. If no events have so far occurred, then,
52 assuming a blocking file descriptor, read(2) will block until at least
53 one event occurs (unless interrupted by a signal, in which case the
54 call fails with the error EINTR; see signal(7)).
55
56 Each successful read(2) returns a buffer containing one or more of the
57 following structures:
58
59 struct inotify_event {
60 int wd; /* Watch descriptor */
61 uint32_t mask; /* Mask describing event */
62 uint32_t cookie; /* Unique cookie associating related
63 events (for rename(2)) */
64 uint32_t len; /* Size of name field */
65 char name[]; /* Optional null-terminated name */
66 };
67
68 wd identifies the watch for which this event occurs. It is one of the
69 watch descriptors returned by a previous call to inotify_add_watch(2).
70
71 mask contains bits that describe the event that occurred (see below).
72
73 cookie is a unique integer that connects related events. Currently,
74 this is used only for rename events, and allows the resulting pair of
75 IN_MOVED_FROM and IN_MOVED_TO events to be connected by the applica‐
76 tion. For all other event types, cookie is set to 0.
77
78 The name field is present only when an event is returned for a file
79 inside a watched directory; it identifies the filename within the
80 watched directory. This filename is null-terminated, and may include
81 further null bytes ('\0') to align subsequent reads to a suitable
82 address boundary.
83
84 The len field counts all of the bytes in name, including the null
85 bytes; the length of each inotify_event structure is thus sizeof(struct
86 inotify_event)+len.
87
88 The behavior when the buffer given to read(2) is too small to return
89 information about the next event depends on the kernel version: in ker‐
90 nels before 2.6.21, read(2) returns 0; since kernel 2.6.21, read(2)
91 fails with the error EINVAL. Specifying a buffer of size
92
93 sizeof(struct inotify_event) + NAME_MAX + 1
94
95 will be sufficient to read at least one event.
96
97 inotify events
98 The inotify_add_watch(2) mask argument and the mask field of the ino‐
99 tify_event structure returned when read(2)ing an inotify file descrip‐
100 tor are both bit masks identifying inotify events. The following bits
101 can be specified in mask when calling inotify_add_watch(2) and may be
102 returned in the mask field returned by read(2):
103
104 IN_ACCESS (+)
105 File was accessed (e.g., read(2), execve(2)).
106
107 IN_ATTRIB (*)
108 Metadata changed—for example, permissions (e.g., chmod(2)),
109 timestamps (e.g., utimensat(2)), extended attributes (setx‐
110 attr(2)), link count (since Linux 2.6.25; e.g., for the tar‐
111 get of link(2) and for unlink(2)), and user/group ID (e.g.,
112 chown(2)).
113
114 IN_CLOSE_WRITE (+)
115 File opened for writing was closed.
116
117 IN_CLOSE_NOWRITE (*)
118 File or directory not opened for writing was closed.
119
120 IN_CREATE (+)
121 File/directory created in watched directory (e.g., open(2)
122 O_CREAT, mkdir(2), link(2), symlink(2), bind(2) on a UNIX
123 domain socket).
124
125 IN_DELETE (+)
126 File/directory deleted from watched directory.
127
128 IN_DELETE_SELF
129 Watched file/directory was itself deleted. (This event also
130 occurs if an object is moved to another filesystem, since
131 mv(1) in effect copies the file to the other filesystem and
132 then deletes it from the original filesystem.) In addition,
133 an IN_IGNORED event will subsequently be generated for the
134 watch descriptor.
135
136 IN_MODIFY (+)
137 File was modified (e.g., write(2), truncate(2)).
138
139 IN_MOVE_SELF
140 Watched file/directory was itself moved.
141
142 IN_MOVED_FROM (+)
143 Generated for the directory containing the old filename when
144 a file is renamed.
145
146 IN_MOVED_TO (+)
147 Generated for the directory containing the new filename when
148 a file is renamed.
149
150 IN_OPEN (*)
151 File or directory was opened.
152
153 Inotify monitoring is inode-based: when monitoring a file (but not when
154 monitoring the directory containing a file), an event can be generated
155 for activity on any link to the file (in the same or a different direc‐
156 tory).
157
158 When monitoring a directory:
159
160 * the events marked above with an asterisk (*) can occur both for the
161 directory itself and for objects inside the directory; and
162
163 * the events marked with a plus sign (+) occur only for objects inside
164 the directory (not for the directory itself).
165
166 Note: when monitoring a directory, events are not generated for the
167 files inside the directory when the events are performed via a pathname
168 (i.e., a link) that lies outside the monitored directory.
169
170 When events are generated for objects inside a watched directory, the
171 name field in the returned inotify_event structure identifies the name
172 of the file within the directory.
173
174 The IN_ALL_EVENTS macro is defined as a bit mask of all of the above
175 events. This macro can be used as the mask argument when calling ino‐
176 tify_add_watch(2).
177
178 Two additional convenience macros are defined:
179
180 IN_MOVE
181 Equates to IN_MOVED_FROM | IN_MOVED_TO.
182
183 IN_CLOSE
184 Equates to IN_CLOSE_WRITE | IN_CLOSE_NOWRITE.
185
186 The following further bits can be specified in mask when calling ino‐
187 tify_add_watch(2):
188
189 IN_DONT_FOLLOW (since Linux 2.6.15)
190 Don't dereference pathname if it is a symbolic link.
191
192 IN_EXCL_UNLINK (since Linux 2.6.36)
193 By default, when watching events on the children of a direc‐
194 tory, events are generated for children even after they have
195 been unlinked from the directory. This can result in large
196 numbers of uninteresting events for some applications (e.g.,
197 if watching /tmp, in which many applications create tempo‐
198 rary files whose names are immediately unlinked). Specify‐
199 ing IN_EXCL_UNLINK changes the default behavior, so that
200 events are not generated for children after they have been
201 unlinked from the watched directory.
202
203 IN_MASK_ADD
204 If a watch instance already exists for the filesystem object
205 corresponding to pathname, add (OR) the events in mask to
206 the watch mask (instead of replacing the mask); the error
207 EINVAL results if IN_MASK_CREATE is also specified.
208
209 IN_ONESHOT
210 Monitor the filesystem object corresponding to pathname for
211 one event, then remove from watch list.
212
213 IN_ONLYDIR (since Linux 2.6.15)
214 Watch pathname only if it is a directory; the error ENOTDIR
215 results if pathname is not a directory. Using this flag
216 provides an application with a race-free way of ensuring
217 that the monitored object is a directory.
218
219 IN_MASK_CREATE (since Linux 4.18)
220 Watch pathname only if it does not already have a watch
221 associated with it; the error EEXIST results if pathname is
222 already being watched.
223
224 Using this flag provides an application with a way of ensur‐
225 ing that new watches do not modify existing ones. This is
226 useful because multiple paths may refer to the same inode,
227 and multiple calls to inotify_add_watch(2) without this flag
228 may clobber existing watch masks.
229
230 The following bits may be set in the mask field returned by read(2):
231
232 IN_IGNORED
233 Watch was removed explicitly (inotify_rm_watch(2)) or auto‐
234 matically (file was deleted, or filesystem was unmounted).
235 See also BUGS.
236
237 IN_ISDIR
238 Subject of this event is a directory.
239
240 IN_Q_OVERFLOW
241 Event queue overflowed (wd is -1 for this event).
242
243 IN_UNMOUNT
244 Filesystem containing watched object was unmounted. In
245 addition, an IN_IGNORED event will subsequently be generated
246 for the watch descriptor.
247
248 Examples
249 Suppose an application is watching the directory dir and the file
250 dir/myfile for all events. The examples below show some events that
251 will be generated for these two objects.
252
253 fd = open("dir/myfile", O_RDWR);
254 Generates IN_OPEN events for both dir and dir/myfile.
255
256 read(fd, buf, count);
257 Generates IN_ACCESS events for both dir and dir/myfile.
258
259 write(fd, buf, count);
260 Generates IN_MODIFY events for both dir and dir/myfile.
261
262 fchmod(fd, mode);
263 Generates IN_ATTRIB events for both dir and dir/myfile.
264
265 close(fd);
266 Generates IN_CLOSE_WRITE events for both dir and dir/myfile.
267
268 Suppose an application is watching the directories dir1 and dir2, and
269 the file dir1/myfile. The following examples show some events that may
270 be generated.
271
272 link("dir1/myfile", "dir2/new");
273 Generates an IN_ATTRIB event for myfile and an IN_CREATE
274 event for dir2.
275
276 rename("dir1/myfile", "dir2/myfile");
277 Generates an IN_MOVED_FROM event for dir1, an IN_MOVED_TO
278 event for dir2, and an IN_MOVE_SELF event for myfile. The
279 IN_MOVED_FROM and IN_MOVED_TO events will have the same
280 cookie value.
281
282 Suppose that dir1/xx and dir2/yy are (the only) links to the same file,
283 and an application is watching dir1, dir2, dir1/xx, and dir2/yy. Exe‐
284 cuting the following calls in the order given below will generate the
285 following events:
286
287 unlink("dir2/yy");
288 Generates an IN_ATTRIB event for xx (because its link count
289 changes) and an IN_DELETE event for dir2.
290
291 unlink("dir1/xx");
292 Generates IN_ATTRIB, IN_DELETE_SELF, and IN_IGNORED events
293 for xx, and an IN_DELETE event for dir1.
294
295 Suppose an application is watching the directory dir and (the empty)
296 directory dir/subdir. The following examples show some events that may
297 be generated.
298
299 mkdir("dir/new", mode);
300 Generates an IN_CREATE | IN_ISDIR event for dir.
301
302 rmdir("dir/subdir");
303 Generates IN_DELETE_SELF and IN_IGNORED events for subdir,
304 and an IN_DELETE | IN_ISDIR event for dir.
305
306 /proc interfaces
307 The following interfaces can be used to limit the amount of kernel mem‐
308 ory consumed by inotify:
309
310 /proc/sys/fs/inotify/max_queued_events
311 The value in this file is used when an application calls ino‐
312 tify_init(2) to set an upper limit on the number of events that
313 can be queued to the corresponding inotify instance. Events in
314 excess of this limit are dropped, but an IN_Q_OVERFLOW event is
315 always generated.
316
317 /proc/sys/fs/inotify/max_user_instances
318 This specifies an upper limit on the number of inotify instances
319 that can be created per real user ID.
320
321 /proc/sys/fs/inotify/max_user_watches
322 This specifies an upper limit on the number of watches that can
323 be created per real user ID.
324
326 Inotify was merged into the 2.6.13 Linux kernel. The required library
327 interfaces were added to glibc in version 2.4. (IN_DONT_FOLLOW,
328 IN_MASK_ADD, and IN_ONLYDIR were added in glibc version 2.5.)
329
331 The inotify API is Linux-specific.
332
334 Inotify file descriptors can be monitored using select(2), poll(2), and
335 epoll(7). When an event is available, the file descriptor indicates as
336 readable.
337
338 Since Linux 2.6.25, signal-driven I/O notification is available for
339 inotify file descriptors; see the discussion of F_SETFL (for setting
340 the O_ASYNC flag), F_SETOWN, and F_SETSIG in fcntl(2). The siginfo_t
341 structure (described in sigaction(2)) that is passed to the signal han‐
342 dler has the following fields set: si_fd is set to the inotify file
343 descriptor number; si_signo is set to the signal number; si_code is set
344 to POLL_IN; and POLLIN is set in si_band.
345
346 If successive output inotify events produced on the inotify file
347 descriptor are identical (same wd, mask, cookie, and name), then they
348 are coalesced into a single event if the older event has not yet been
349 read (but see BUGS). This reduces the amount of kernel memory required
350 for the event queue, but also means that an application can't use ino‐
351 tify to reliably count file events.
352
353 The events returned by reading from an inotify file descriptor form an
354 ordered queue. Thus, for example, it is guaranteed that when renaming
355 from one directory to another, events will be produced in the correct
356 order on the inotify file descriptor.
357
358 The set of watch descriptors that is being monitored via an inotify
359 file descriptor can be viewed via the entry for the inotify file
360 descriptor in the process's /proc/[pid]/fdinfo directory. See proc(5)
361 for further details. The FIONREAD ioctl(2) returns the number of bytes
362 available to read from an inotify file descriptor.
363
364 Limitations and caveats
365 The inotify API provides no information about the user or process that
366 triggered the inotify event. In particular, there is no easy way for a
367 process that is monitoring events via inotify to distinguish events
368 that it triggers itself from those that are triggered by other pro‐
369 cesses.
370
371 Inotify reports only events that a user-space program triggers through
372 the filesystem API. As a result, it does not catch remote events that
373 occur on network filesystems. (Applications must fall back to polling
374 the filesystem to catch such events.) Furthermore, various pseudo-
375 filesystems such as /proc, /sys, and /dev/pts are not monitorable with
376 inotify.
377
378 The inotify API does not report file accesses and modifications that
379 may occur because of mmap(2), msync(2), and munmap(2).
380
381 The inotify API identifies affected files by filename. However, by the
382 time an application processes an inotify event, the filename may
383 already have been deleted or renamed.
384
385 The inotify API identifies events via watch descriptors. It is the
386 application's responsibility to cache a mapping (if one is needed)
387 between watch descriptors and pathnames. Be aware that directory
388 renamings may affect multiple cached pathnames.
389
390 Inotify monitoring of directories is not recursive: to monitor subdi‐
391 rectories under a directory, additional watches must be created. This
392 can take a significant amount time for large directory trees.
393
394 If monitoring an entire directory subtree, and a new subdirectory is
395 created in that tree or an existing directory is renamed into that
396 tree, be aware that by the time you create a watch for the new subdi‐
397 rectory, new files (and subdirectories) may already exist inside the
398 subdirectory. Therefore, you may want to scan the contents of the sub‐
399 directory immediately after adding the watch (and, if desired, recur‐
400 sively add watches for any subdirectories that it contains).
401
402 Note that the event queue can overflow. In this case, events are lost.
403 Robust applications should handle the possibility of lost events grace‐
404 fully. For example, it may be necessary to rebuild part or all of the
405 application cache. (One simple, but possibly expensive, approach is to
406 close the inotify file descriptor, empty the cache, create a new ino‐
407 tify file descriptor, and then re-create watches and cache entries for
408 the objects to be monitored.)
409
410 If a filesystem is mounted on top of a monitored directory, no event is
411 generated, and no events are generated for objects immediately under
412 the new mount point. If the filesystem is subsequently unmounted,
413 events will subsequently be generated for the directory and the objects
414 it contains.
415
416 Dealing with rename() events
417 As noted above, the IN_MOVED_FROM and IN_MOVED_TO event pair that is
418 generated by rename(2) can be matched up via their shared cookie value.
419 However, the task of matching has some challenges.
420
421 These two events are usually consecutive in the event stream available
422 when reading from the inotify file descriptor. However, this is not
423 guaranteed. If multiple processes are triggering events for monitored
424 objects, then (on rare occasions) an arbitrary number of other events
425 may appear between the IN_MOVED_FROM and IN_MOVED_TO events. Further‐
426 more, it is not guaranteed that the event pair is atomically inserted
427 into the queue: there may be a brief interval where the IN_MOVED_FROM
428 has appeared, but the IN_MOVED_TO has not.
429
430 Matching up the IN_MOVED_FROM and IN_MOVED_TO event pair generated by
431 rename(2) is thus inherently racy. (Don't forget that if an object is
432 renamed outside of a monitored directory, there may not even be an
433 IN_MOVED_TO event.) Heuristic approaches (e.g., assume the events are
434 always consecutive) can be used to ensure a match in most cases, but
435 will inevitably miss some cases, causing the application to perceive
436 the IN_MOVED_FROM and IN_MOVED_TO events as being unrelated. If watch
437 descriptors are destroyed and re-created as a result, then those watch
438 descriptors will be inconsistent with the watch descriptors in any
439 pending events. (Re-creating the inotify file descriptor and rebuild‐
440 ing the cache may be useful to deal with this scenario.)
441
442 Applications should also allow for the possibility that the
443 IN_MOVED_FROM event was the last event that could fit in the buffer
444 returned by the current call to read(2), and the accompanying
445 IN_MOVED_TO event might be fetched only on the next read(2), which
446 should be done with a (small) timeout to allow for the fact that inser‐
447 tion of the IN_MOVED_FROM-IN_MOVED_TO event pair is not atomic, and
448 also the possibility that there may not be any IN_MOVED_TO event.
449
451 Before Linux 3.19, fallocate(2) did not create any inotify events.
452 Since Linux 3.19, calls to fallocate(2) generate IN_MODIFY events.
453
454 In kernels before 2.6.16, the IN_ONESHOT mask flag does not work.
455
456 As originally designed and implemented, the IN_ONESHOT flag did not
457 cause an IN_IGNORED event to be generated when the watch was dropped
458 after one event. However, as an unintended effect of other changes,
459 since Linux 2.6.36, an IN_IGNORED event is generated in this case.
460
461 Before kernel 2.6.25, the kernel code that was intended to coalesce
462 successive identical events (i.e., the two most recent events could
463 potentially be coalesced if the older had not yet been read) instead
464 checked if the most recent event could be coalesced with the oldest
465 unread event.
466
467 When a watch descriptor is removed by calling inotify_rm_watch(2) (or
468 because a watch file is deleted or the filesystem that contains it is
469 unmounted), any pending unread events for that watch descriptor remain
470 available to read. As watch descriptors are subsequently allocated
471 with inotify_add_watch(2), the kernel cycles through the range of pos‐
472 sible watch descriptors (0 to INT_MAX) incrementally. When allocating
473 a free watch descriptor, no check is made to see whether that watch
474 descriptor number has any pending unread events in the inotify queue.
475 Thus, it can happen that a watch descriptor is reallocated even when
476 pending unread events exist for a previous incarnation of that watch
477 descriptor number, with the result that the application might then read
478 those events and interpret them as belonging to the file associated
479 with the newly recycled watch descriptor. In practice, the likelihood
480 of hitting this bug may be extremely low, since it requires that an
481 application cycle through INT_MAX watch descriptors, release a watch
482 descriptor while leaving unread events for that watch descriptor in the
483 queue, and then recycle that watch descriptor. For this reason, and
484 because there have been no reports of the bug occurring in real-world
485 applications, as of Linux 3.15, no kernel changes have yet been made to
486 eliminate this possible bug.
487
489 The following program demonstrates the usage of the inotify API. It
490 marks the directories passed as a command-line arguments and waits for
491 events of type IN_OPEN, IN_CLOSE_NOWRITE and IN_CLOSE_WRITE.
492
493 The following output was recorded while editing the file
494 /home/user/temp/foo and listing directory /tmp. Before the file and
495 the directory were opened, IN_OPEN events occurred. After the file was
496 closed, an IN_CLOSE_WRITE event occurred. After the directory was
497 closed, an IN_CLOSE_NOWRITE event occurred. Execution of the program
498 ended when the user pressed the ENTER key.
499
500 Example output
501 $ ./a.out /tmp /home/user/temp
502 Press enter key to terminate.
503 Listening for events.
504 IN_OPEN: /home/user/temp/foo [file]
505 IN_CLOSE_WRITE: /home/user/temp/foo [file]
506 IN_OPEN: /tmp/ [directory]
507 IN_CLOSE_NOWRITE: /tmp/ [directory]
508
509 Listening for events stopped.
510
511 Program source
512
513 #include <errno.h>
514 #include <poll.h>
515 #include <stdio.h>
516 #include <stdlib.h>
517 #include <sys/inotify.h>
518 #include <unistd.h>
519 #include <string.h>
520
521 /* Read all available inotify events from the file descriptor 'fd'.
522 wd is the table of watch descriptors for the directories in argv.
523 argc is the length of wd and argv.
524 argv is the list of watched directories.
525 Entry 0 of wd and argv is unused. */
526
527 static void
528 handle_events(int fd, int *wd, int argc, char* argv[])
529 {
530 /* Some systems cannot read integer variables if they are not
531 properly aligned. On other systems, incorrect alignment may
532 decrease performance. Hence, the buffer used for reading from
533 the inotify file descriptor should have the same alignment as
534 struct inotify_event. */
535
536 char buf[4096]
537 __attribute__ ((aligned(__alignof__(struct inotify_event))));
538 const struct inotify_event *event;
539 int i;
540 ssize_t len;
541 char *ptr;
542
543 /* Loop while events can be read from inotify file descriptor. */
544
545 for (;;) {
546
547 /* Read some events. */
548
549 len = read(fd, buf, sizeof buf);
550 if (len == -1 && errno != EAGAIN) {
551 perror("read");
552 exit(EXIT_FAILURE);
553 }
554
555 /* If the nonblocking read() found no events to read, then
556 it returns -1 with errno set to EAGAIN. In that case,
557 we exit the loop. */
558
559 if (len <= 0)
560 break;
561
562 /* Loop over all events in the buffer */
563
564 for (ptr = buf; ptr < buf + len;
565 ptr += sizeof(struct inotify_event) + event->len) {
566
567 event = (const struct inotify_event *) ptr;
568
569 /* Print event type */
570
571 if (event->mask & IN_OPEN)
572 printf("IN_OPEN: ");
573 if (event->mask & IN_CLOSE_NOWRITE)
574 printf("IN_CLOSE_NOWRITE: ");
575 if (event->mask & IN_CLOSE_WRITE)
576 printf("IN_CLOSE_WRITE: ");
577
578 /* Print the name of the watched directory */
579
580 for (i = 1; i < argc; ++i) {
581 if (wd[i] == event->wd) {
582 printf("%s/", argv[i]);
583 break;
584 }
585 }
586
587 /* Print the name of the file */
588
589 if (event->len)
590 printf("%s", event->name);
591
592 /* Print type of filesystem object */
593
594 if (event->mask & IN_ISDIR)
595 printf(" [directory]\n");
596 else
597 printf(" [file]\n");
598 }
599 }
600 }
601
602 int
603 main(int argc, char* argv[])
604 {
605 char buf;
606 int fd, i, poll_num;
607 int *wd;
608 nfds_t nfds;
609 struct pollfd fds[2];
610
611 if (argc < 2) {
612 printf("Usage: %s PATH [PATH ...]\n", argv[0]);
613 exit(EXIT_FAILURE);
614 }
615
616 printf("Press ENTER key to terminate.\n");
617
618 /* Create the file descriptor for accessing the inotify API */
619
620 fd = inotify_init1(IN_NONBLOCK);
621 if (fd == -1) {
622 perror("inotify_init1");
623 exit(EXIT_FAILURE);
624 }
625
626 /* Allocate memory for watch descriptors */
627
628 wd = calloc(argc, sizeof(int));
629 if (wd == NULL) {
630 perror("calloc");
631 exit(EXIT_FAILURE);
632 }
633
634 /* Mark directories for events
635 - file was opened
636 - file was closed */
637
638 for (i = 1; i < argc; i++) {
639 wd[i] = inotify_add_watch(fd, argv[i],
640 IN_OPEN | IN_CLOSE);
641 if (wd[i] == -1) {
642 fprintf(stderr, "Cannot watch '%s': %s\n",
643 argv[i], strerror(errno));
644 exit(EXIT_FAILURE);
645 }
646 }
647
648 /* Prepare for polling */
649
650 nfds = 2;
651
652 /* Console input */
653
654 fds[0].fd = STDIN_FILENO;
655 fds[0].events = POLLIN;
656
657 /* Inotify input */
658
659 fds[1].fd = fd;
660 fds[1].events = POLLIN;
661
662 /* Wait for events and/or terminal input */
663
664 printf("Listening for events.\n");
665 while (1) {
666 poll_num = poll(fds, nfds, -1);
667 if (poll_num == -1) {
668 if (errno == EINTR)
669 continue;
670 perror("poll");
671 exit(EXIT_FAILURE);
672 }
673
674 if (poll_num > 0) {
675
676 if (fds[0].revents & POLLIN) {
677
678 /* Console input is available. Empty stdin and quit */
679
680 while (read(STDIN_FILENO, &buf, 1) > 0 && buf != '\n')
681 continue;
682 break;
683 }
684
685 if (fds[1].revents & POLLIN) {
686
687 /* Inotify events are available */
688
689 handle_events(fd, wd, argc, argv);
690 }
691 }
692 }
693
694 printf("Listening for events stopped.\n");
695
696 /* Close inotify file descriptor */
697
698 close(fd);
699
700 free(wd);
701 exit(EXIT_SUCCESS);
702 }
703
705 inotifywait(1), inotifywatch(1), inotify_add_watch(2), inotify_init(2),
706 inotify_init1(2), inotify_rm_watch(2), read(2), stat(2), fanotify(7)
707
708 Documentation/filesystems/inotify.txt in the Linux kernel source tree
709
711 This page is part of release 5.07 of the Linux man-pages project. A
712 description of the project, information about reporting bugs, and the
713 latest version of this page, can be found at
714 https://www.kernel.org/doc/man-pages/.
715
716
717
718Linux 2020-06-09 INOTIFY(7)