]>
Commit | Line | Data |
---|---|---|
597aaea2 | 1 | .\" Copyright (C) 2013, Heinrich Schuchardt <xypron.glpk@gmx.de> |
89613d50 | 2 | .\" and Copyright (C) 2014, Michael Kerrisk <mtk.manpages@gmail.com> |
597aaea2 HS |
3 | .\" |
4 | .\" %%%LICENSE_START(VERBATIM) | |
5 | .\" Permission is granted to make and distribute verbatim copies of this | |
6 | .\" manual provided the copyright notice and this permission notice are | |
7 | .\" preserved on all copies. | |
8 | .\" | |
9 | .\" Permission is granted to copy and distribute modified versions of | |
10 | .\" this manual under the conditions for verbatim copying, provided that | |
11 | .\" the entire resulting derived work is distributed under the terms of | |
12 | .\" a permission notice identical to this one. | |
13 | .\" | |
14 | .\" Since the Linux kernel and libraries are constantly changing, this | |
15 | .\" manual page may be incorrect or out-of-date. The author(s) assume. | |
16 | .\" no responsibility for errors or omissions, or for damages resulting. | |
17 | .\" from the use of the information contained herein. The author(s) may. | |
18 | .\" not have taken the same level of care in the production of this. | |
19 | .\" manual, which is licensed free of charge, as they might when working. | |
20 | .\" professionally. | |
21 | .\" | |
22 | .\" Formatted or processed versions of this manual, if unaccompanied by | |
23 | .\" the source, must acknowledge the copyright and authors of this work. | |
24 | .\" %%%LICENSE_END | |
9ba01802 | 25 | .TH FANOTIFY 7 2019-03-06 "Linux" "Linux Programmer's Manual" |
597aaea2 HS |
26 | .SH NAME |
27 | fanotify \- monitoring filesystem events | |
28 | .SH DESCRIPTION | |
1b24e2ee MK |
29 | The fanotify API provides notification and interception of |
30 | filesystem events. | |
597aaea2 HS |
31 | Use cases include virus scanning and hierarchical storage management. |
32 | Currently, only a limited set of events is supported. | |
7ea227bd | 33 | In particular, there is no support for create, delete, and move events. |
d9b086d6 MK |
34 | (See |
35 | .BR inotify (7) | |
36 | for details of an API that does notify those events.) | |
a721e8b2 | 37 | .PP |
597aaea2 HS |
38 | Additional capabilities compared to the |
39 | .BR inotify (7) | |
4a57583f MK |
40 | API include the ability to monitor all of the objects |
41 | in a mounted filesystem, | |
42 | the ability to make access permission decisions, and the | |
597aaea2 | 43 | possibility to read or modify files before access by other applications. |
a721e8b2 | 44 | .PP |
597aaea2 HS |
45 | The following system calls are used with this API: |
46 | .BR fanotify_init (2), | |
47 | .BR fanotify_mark (2), | |
597aaea2 HS |
48 | .BR read (2), |
49 | .BR write (2), | |
50 | and | |
51 | .BR close (2). | |
6c693f6d | 52 | .SS fanotify_init(), fanotify_mark(), and notification groups |
397ff1fd | 53 | The |
597aaea2 | 54 | .BR fanotify_init (2) |
397ff1fd MK |
55 | system call creates and initializes an fanotify notification group |
56 | and returns a file descriptor referring to it. | |
597aaea2 | 57 | .PP |
7ea227bd | 58 | An fanotify notification group is a kernel-internal object that holds |
953d1e07 | 59 | a list of files, directories, filesystems, and mount points for which |
b2f8214d | 60 | events shall be created. |
597aaea2 | 61 | .PP |
7ea227bd MK |
62 | For each entry in an fanotify notification group, two bit masks exist: the |
63 | .I mark | |
64 | mask and the | |
65 | .I ignore | |
66 | mask. | |
67 | The mark mask defines file activities for which an event shall be created. | |
68 | The ignore mask defines activities for which no event shall be generated. | |
953d1e07 | 69 | Having these two types of masks permits a filesystem, mount point, or |
b2f8214d AG |
70 | directory to be marked for receiving events, while at the same time |
71 | ignoring events for specific objects under a mount point or directory. | |
597aaea2 | 72 | .PP |
ffb30e75 | 73 | The |
6c693f6d | 74 | .BR fanotify_mark (2) |
b2f8214d AG |
75 | system call adds a file, directory, filesystem or mount point to a |
76 | notification group and specifies which events | |
6c693f6d MK |
77 | shall be reported (or ignored), or removes or modifies such an entry. |
78 | .PP | |
597aaea2 HS |
79 | A possible usage of the ignore mask is for a file cache. |
80 | Events of interest for a file cache are modification of a file and closing | |
81 | of the same. | |
82 | Hence, the cached directory or mount point is to be marked to receive these | |
83 | events. | |
1b24e2ee MK |
84 | After receiving the first event informing that a file has been modified, |
85 | the corresponding cache entry will be invalidated. | |
86 | No further modification events for this file are of interest until the file | |
87 | is closed. | |
597aaea2 | 88 | Hence, the modify event can be added to the ignore mask. |
5e443a5f | 89 | Upon receiving the close event, the modify event can be removed from the |
597aaea2 HS |
90 | ignore mask and the file cache entry can be updated. |
91 | .PP | |
1b24e2ee MK |
92 | The entries in the fanotify notification groups refer to files and |
93 | directories via their inode number and to mounts via their mount ID. | |
7d3c593b | 94 | If files or directories are renamed or moved within the same mount, |
1b24e2ee | 95 | the respective entries survive. |
b2f8214d AG |
96 | If files or directories are deleted or moved to another mount or if |
97 | filesystems or mounts are unmounted, the corresponding entries are deleted. | |
ad02dd1f | 98 | .SS The event queue |
77bba7b5 | 99 | As events occur on the filesystem objects monitored by a notification group, |
c9120323 MK |
100 | the fanotify system generates events that are collected in a queue. |
101 | These events can then be read (using | |
102 | .BR read (2) | |
103 | or similar) | |
104 | from the fanotify file descriptor | |
105 | returned by | |
106 | .BR fanotify_init (2). | |
a721e8b2 | 107 | .PP |
c9120323 | 108 | Two types of events are generated: |
4a57583f MK |
109 | .I notification |
110 | events and | |
111 | .I permission | |
112 | events. | |
c9120323 MK |
113 | Notification events are merely informative |
114 | and require no action to be taken by | |
0a4db6dc MB |
115 | the receiving application with the exception being that the file |
116 | descriptor provided within a generic event must be closed. | |
817c8240 | 117 | The closing of file descriptors for each event applies only to |
0a4db6dc MB |
118 | applications that have initialized fanotify without using |
119 | .BR FAN_REPORT_FID | |
120 | (see below). | |
1b24e2ee MK |
121 | Permission events are requests to the receiving application to decide |
122 | whether permission for a file access shall be granted. | |
597aaea2 HS |
123 | For these events, the recipient must write a response which decides whether |
124 | access is granted or not. | |
a721e8b2 | 125 | .PP |
33022419 MK |
126 | An event is removed from the event queue of the fanotify group |
127 | when it has been read. | |
a6625006 | 128 | Permission events that have been read are kept in an internal list of the |
33022419 MK |
129 | fanotify group until either a permission decision has been taken by |
130 | writing to the fanotify file descriptor or the fanotify file descriptor | |
131 | is closed. | |
ad02dd1f | 132 | .SS Reading fanotify events |
597aaea2 HS |
133 | Calling |
134 | .BR read (2) | |
135 | for the file descriptor returned by | |
136 | .BR fanotify_init (2) | |
137 | blocks (if the flag | |
138 | .B FAN_NONBLOCK | |
139 | is not specified in the call to | |
140 | .BR fanotify_init (2)) | |
141 | until either a file event occurs or the call is interrupted by a signal | |
142 | (see | |
143 | .BR signal (7)). | |
a721e8b2 | 144 | .PP |
f5230cf1 | 145 | The use of the |
0a4db6dc | 146 | .BR FAN_REPORT_FID |
f5230cf1 | 147 | flag in |
0a4db6dc | 148 | .BR fanotify_init (2) |
58ba48e4 | 149 | influences what data structures are returned to the event listener for each |
f5230cf1 | 150 | event. |
597aaea2 | 151 | After a successful |
7ea227bd | 152 | .BR read (2), |
597aaea2 | 153 | the read buffer contains one or more of the following structures: |
a721e8b2 | 154 | .PP |
597aaea2 | 155 | .in +4n |
b8302363 | 156 | .EX |
597aaea2 HS |
157 | struct fanotify_event_metadata { |
158 | __u32 event_len; | |
159 | __u8 vers; | |
160 | __u8 reserved; | |
161 | __u16 metadata_len; | |
162 | __aligned_u64 mask; | |
163 | __s32 fd; | |
164 | __s32 pid; | |
165 | }; | |
b8302363 | 166 | .EE |
597aaea2 | 167 | .in |
f2ac23e7 | 168 | .PP |
817c8240 | 169 | In the case where |
0a4db6dc MB |
170 | .BR FAN_REPORT_FID |
171 | is supplied as one of the flags to | |
172 | .BR fanotify_init (2), | |
173 | you should also expect to receive the structure detailed below following | |
174 | the generic | |
175 | .I fanotify_event_metadata | |
176 | structure within the read buffer: | |
177 | .PP | |
178 | .in +4n | |
179 | .EX | |
180 | struct fanotify_event_info_fid { | |
181 | struct fanotify_event_info_header hdr; | |
182 | __kernel_fsid_t fsid; | |
183 | unsigned char file_handle[0]; | |
184 | }; | |
185 | .EE | |
186 | .in | |
187 | .PP | |
3253bbc3 MK |
188 | For performance reasons, it is recommended to use a large |
189 | buffer size (for example, 4096 bytes), | |
190 | so that multiple events can be retrieved by a single | |
191 | .BR read (2). | |
a721e8b2 | 192 | .PP |
3253bbc3 MK |
193 | The return value of |
194 | .BR read (2) | |
195 | is the number of bytes placed in the buffer, | |
f96adfdc | 196 | or \-1 in case of an error (but see BUGS). |
a721e8b2 | 197 | .PP |
4a57583f MK |
198 | The fields of the |
199 | .I fanotify_event_metadata | |
200 | structure are as follows: | |
9d76d630 | 201 | .TP |
597aaea2 | 202 | .I event_len |
1b24e2ee MK |
203 | This is the length of the data for the current event and the offset |
204 | to the next event in the buffer. | |
0a4db6dc MB |
205 | Without |
206 | .BR FAN_REPORT_FID , | |
207 | the value of | |
597aaea2 HS |
208 | .I event_len |
209 | is always | |
210 | .BR FAN_EVENT_METADATA_LEN . | |
0a4db6dc MB |
211 | With |
212 | .BR FAN_REPORT_FID , | |
213 | .I event_len | |
214 | also includes the variable length file identifier. | |
597aaea2 HS |
215 | .TP |
216 | .I vers | |
6d8c5d01 | 217 | This field holds a version number for the structure. |
597aaea2 HS |
218 | It must be compared to |
219 | .B FANOTIFY_METADATA_VERSION | |
29c0586f | 220 | to verify that the structures returned at run time match |
6d8c5d01 | 221 | the structures defined at compile time. |
597aaea2 HS |
222 | In case of a mismatch, the application should abandon trying to use the |
223 | fanotify file descriptor. | |
224 | .TP | |
225 | .I reserved | |
226 | This field is not used. | |
227 | .TP | |
228 | .I metadata_len | |
229 | This is the length of the structure. | |
1b24e2ee MK |
230 | The field was introduced to facilitate the implementation of |
231 | optional headers per event type. | |
597aaea2 HS |
232 | No such optional headers exist in the current implementation. |
233 | .TP | |
234 | .I mask | |
4a57583f | 235 | This is a bit mask describing the event (see below). |
597aaea2 HS |
236 | .TP |
237 | .I fd | |
238 | This is an open file descriptor for the object being accessed, or | |
239 | .B FAN_NOFD | |
240 | if a queue overflow occurred. | |
0a4db6dc MB |
241 | If the fanotify file descriptor has been initialized using |
242 | .BR FAN_REPORT_FID , | |
243 | applications should expect this value to be set to | |
244 | .B FAN_NOFD | |
245 | for each event that is received. | |
1b24e2ee MK |
246 | The file descriptor can be used to access the contents |
247 | of the monitored file or directory. | |
4a57583f MK |
248 | The reading application is responsible for closing this file descriptor. |
249 | .IP | |
a4cd12a9 | 250 | When calling |
ce87be97 | 251 | .BR fanotify_init (2), |
a4cd12a9 MK |
252 | the caller may specify (via the |
253 | .I event_f_flags | |
254 | argument) various file status flags that are to be set | |
255 | on the open file description that corresponds to this file descriptor. | |
256 | In addition, the (kernel-internal) | |
597aaea2 | 257 | .B FMODE_NONOTIFY |
a4cd12a9 | 258 | file status flag is set on the open file description. |
597aaea2 HS |
259 | This flag suppresses fanotify event generation. |
260 | Hence, when the receiver of the fanotify event accesses the notified file or | |
261 | directory using this file descriptor, no additional events will be created. | |
597aaea2 HS |
262 | .TP |
263 | .I pid | |
ebfb6fee | 264 | If flag |
265 | .B FAN_REPORT_TID | |
266 | was set in | |
267 | .BR fanotify_init (2), | |
268 | this is the TID of the thread that caused the event. | |
269 | Otherwise, this the PID of the process that caused the event. | |
270 | .PP | |
1b24e2ee MK |
271 | A program listening to fanotify events can compare this PID |
272 | to the PID returned by | |
597aaea2 | 273 | .BR getpid (2), |
1b24e2ee | 274 | to determine whether the event is caused by the listener itself, |
4a57583f | 275 | or is due to a file access by another process. |
597aaea2 HS |
276 | .PP |
277 | The bit mask in | |
278 | .I mask | |
4a57583f | 279 | indicates which events have occurred for a single filesystem object. |
29325644 | 280 | Multiple bits may be set in this mask, |
77bba7b5 | 281 | if more than one event occurred for the monitored filesystem object. |
75c3e3bd MK |
282 | In particular, |
283 | consecutive events for the same filesystem object and originating from the | |
284 | same process may be merged into a single event, with the exception that two | |
285 | permission events are never merged into one queue entry. | |
286 | .PP | |
29325644 MK |
287 | The bits that may appear in |
288 | .I mask | |
289 | are as follows: | |
597aaea2 HS |
290 | .TP |
291 | .B FAN_ACCESS | |
292 | A file or a directory (but see BUGS) was accessed (read). | |
293 | .TP | |
294 | .B FAN_OPEN | |
295 | A file or a directory was opened. | |
296 | .TP | |
fc37d2f1 MB |
297 | .B FAN_OPEN_EXEC |
298 | A file was opened with the intent to be executed. | |
fd1eb8a7 | 299 | See NOTES in |
fc37d2f1 MB |
300 | .BR fanotify_mark (2) |
301 | for additional details. | |
302 | .TP | |
0a4db6dc MB |
303 | .B FAN_ATTRIB |
304 | A file or directory metadata was changed. | |
305 | .TP | |
306 | .B FAN_CREATE | |
307 | A child file or directory was created in a watched parent. | |
308 | .TP | |
309 | .B FAN_DELETE | |
310 | A child file or directory was deleted in a watched parent. | |
311 | .TP | |
312 | .B FAN_DELETE_SELF | |
313 | A watched file or directory was deleted. | |
314 | .TP | |
315 | .B FAN_MOVED_FROM | |
316 | A file or directory has been moved from a watched parent directory. | |
317 | .TP | |
318 | .B FAN_MOVED_TO | |
319 | A file or directory has been moved to a watched parent directory. | |
320 | .TP | |
321 | .B FAN_MOVE_SELF | |
322 | A watched file or directory was moved. | |
323 | .TP | |
597aaea2 HS |
324 | .B FAN_MODIFY |
325 | A file was modified. | |
326 | .TP | |
327 | .B FAN_CLOSE_WRITE | |
328 | A file that was opened for writing | |
329 | .RB ( O_WRONLY | |
330 | or | |
331 | .BR O_RDWR ) | |
332 | was closed. | |
333 | .TP | |
334 | .B FAN_CLOSE_NOWRITE | |
02a18e0f | 335 | A file or directory that was opened read-only |
597aaea2 | 336 | .RB ( O_RDONLY ) |
02a18e0f | 337 | was closed. |
597aaea2 HS |
338 | .TP |
339 | .B FAN_Q_OVERFLOW | |
340 | The event queue exceeded the limit of 16384 entries. | |
4a57583f MK |
341 | This limit can be overridden by specifying the |
342 | .BR FAN_UNLIMITED_QUEUE | |
343 | flag when calling | |
344 | .BR fanotify_init (2). | |
597aaea2 HS |
345 | .TP |
346 | .B FAN_ACCESS_PERM | |
347 | An application wants to read a file or directory, for example using | |
348 | .BR read (2) | |
349 | or | |
350 | .BR readdir (2). | |
4a57583f MK |
351 | The reader must write a response (as described below) |
352 | that determines whether the permission to | |
597aaea2 HS |
353 | access the filesystem object shall be granted. |
354 | .TP | |
355 | .B FAN_OPEN_PERM | |
356 | An application wants to open a file or directory. | |
357 | The reader must write a response that determines whether the permission to | |
358 | open the filesystem object shall be granted. | |
fc37d2f1 MB |
359 | .TP |
360 | .B FAN_OPEN_EXEC_PERM | |
361 | An application wants to open a file for execution. | |
362 | The reader must write a response that determines whether the permission to | |
363 | open the filesystem object for execution shall be granted. | |
fd1eb8a7 | 364 | See NOTES in |
fc37d2f1 MB |
365 | .BR fanotify_mark (2) |
366 | for additional details. | |
597aaea2 HS |
367 | .PP |
368 | To check for any close event, the following bit mask may be used: | |
369 | .TP | |
370 | .B FAN_CLOSE | |
f897ec11 | 371 | A file was closed. |
4a57583f | 372 | This is a synonym for: |
a721e8b2 | 373 | .IP |
f897ec11 | 374 | FAN_CLOSE_WRITE | FAN_CLOSE_NOWRITE |
597aaea2 | 375 | .PP |
0a4db6dc MB |
376 | To check for any move event, the following bit mask may be used: |
377 | .TP | |
378 | .B FAN_MOVE | |
379 | A file or directory was moved. | |
380 | This is a synonym for: | |
381 | .IP | |
382 | FAN_MOVED_FROM | FAN_MOVED_TO | |
383 | .PP | |
384 | The fields of the | |
385 | .I fanotify_event_info_fid | |
386 | structure are as follows: | |
387 | .TP | |
388 | .I hdr | |
389 | This is a structure of type | |
390 | .IR fanotify_event_info_header . | |
391 | It is a generic header that contains information used to describe | |
392 | additional information attached to the event. | |
393 | For example, when an fanotify file descriptor is created using | |
817c8240 | 394 | .BR FAN_REPORT_FID , |
0a4db6dc MB |
395 | the |
396 | .I info_type | |
397 | field of this header is set to | |
398 | .BR FAN_EVENT_INFO_TYPE_FID . | |
399 | Event listeners can use this field to check that the additional | |
400 | information received for an event is of the correct type. | |
401 | Additionally, the | |
402 | .I fanotify_event_info_header | |
403 | also contains a | |
404 | .I len | |
405 | field. | |
406 | In the current implementation, the value of | |
407 | .I len | |
5ff63f51 | 408 | is always (event_len \- FAN_EVENT_METADATA_LEN). |
0a4db6dc MB |
409 | .TP |
410 | .I fsid | |
411 | This is a unique identifier of the filesystem containing the object | |
412 | associated with the event. | |
413 | It is a structure of type | |
414 | .I __kernel_fsid_t | |
415 | and contains the same value as | |
416 | .I f_fsid | |
417 | when calling | |
418 | .BR statfs (2). | |
419 | .TP | |
420 | .I file_handle | |
421 | This is a variable length structure of type | |
422 | .IR file_handle . | |
423 | It is an opaque handle that corresponds to a specified object on a | |
424 | filesystem as returned by | |
817c8240 | 425 | .BR name_to_handle_at (2). |
0a4db6dc MB |
426 | It can be used to uniquely identify a file on a filesystem and can be |
427 | passed as an argument to | |
817c8240 | 428 | .BR open_by_handle_at (2). |
0a4db6dc MB |
429 | Note that for directory entry events, such as |
430 | .BR FAN_CREATE , | |
431 | .BR FAN_DELETE , | |
817c8240 MK |
432 | and |
433 | .BR FAN_MOVE , | |
0a4db6dc MB |
434 | the |
435 | .IR file_handle | |
436 | describes the modified directory and not the created/deleted/moved child | |
437 | object. | |
438 | The events | |
439 | .BR FAN_ATTRIB , | |
817c8240 | 440 | .BR FAN_DELETE_SELF , |
0a4db6dc MB |
441 | and |
442 | .BR FAN_MOVE_SELF | |
443 | will carry the | |
444 | .IR file_handle | |
445 | information for the child object if the child object is being watched. | |
446 | .PP | |
1b24e2ee | 447 | The following macros are provided to iterate over a buffer containing |
4a57583f | 448 | fanotify event metadata returned by a |
597aaea2 | 449 | .BR read (2) |
4a57583f | 450 | from an fanotify file descriptor: |
597aaea2 HS |
451 | .TP |
452 | .B FAN_EVENT_OK(meta, len) | |
453 | This macro checks the remaining length | |
454 | .I len | |
455 | of the buffer | |
456 | .I meta | |
457 | against the length of the metadata structure and the | |
458 | .I event_len | |
459 | field of the first metadata structure in the buffer. | |
460 | .TP | |
461 | .B FAN_EVENT_NEXT(meta, len) | |
98f7d53c | 462 | This macro uses the length indicated in the |
597aaea2 | 463 | .I event_len |
98f7d53c MK |
464 | field of the metadata structure pointed to by |
465 | .IR meta | |
466 | to calculate the address of the next metadata structure that follows | |
467 | .IR meta . | |
468 | .I len | |
469 | is the number of bytes of metadata that currently remain in the buffer. | |
470 | The macro returns a pointer to the next metadata structure that follows | |
471 | .IR meta , | |
472 | and reduces | |
473 | .I len | |
d721b5aa | 474 | by the number of bytes in the metadata structure that |
98f7d53c MK |
475 | has been skipped over (i.e., it subtracts |
476 | .IR meta\->event_len | |
477 | from | |
478 | .IR len ). | |
3c36e635 HS |
479 | .PP |
480 | In addition, there is: | |
481 | .TP | |
482 | .B FAN_EVENT_METADATA_LEN | |
7c0f0ce0 MK |
483 | This macro returns the size (in bytes) of the structure |
484 | .IR fanotify_event_metadata . | |
3c36e635 | 485 | This is the minimum size (and currently the only size) of any event metadata. |
98f7d53c | 486 | .\" |
488cdd81 MK |
487 | .SS Monitoring an fanotify file descriptor for events |
488 | When an fanotify event occurs, the fanotify file descriptor indicates as | |
489 | readable when passed to | |
490 | .BR epoll (7), | |
491 | .BR poll (2), | |
492 | or | |
493 | .BR select (2). | |
88145b29 | 494 | .SS Dealing with permission events |
597aaea2 HS |
495 | For permission events, the application must |
496 | .BR write (2) | |
497 | a structure of the following form to the | |
d3471a46 | 498 | fanotify file descriptor: |
a721e8b2 | 499 | .PP |
597aaea2 | 500 | .in +4n |
b8302363 | 501 | .EX |
597aaea2 HS |
502 | struct fanotify_response { |
503 | __s32 fd; | |
504 | __u32 response; | |
505 | }; | |
b8302363 | 506 | .EE |
597aaea2 | 507 | .in |
d7d24d40 MK |
508 | .PP |
509 | The fields of this structure are as follows: | |
9d76d630 | 510 | .TP |
597aaea2 HS |
511 | .I fd |
512 | This is the file descriptor from the structure | |
513 | .IR fanotify_event_metadata . | |
514 | .TP | |
515 | .I response | |
516 | This field indicates whether or not the permission is to be granted. | |
517 | Its value must be either | |
518 | .B FAN_ALLOW | |
519 | to allow the file operation or | |
520 | .B FAN_DENY | |
521 | to deny the file operation. | |
522 | .PP | |
49894a5a MK |
523 | If access is denied, the requesting application call will receive an |
524 | .BR EPERM | |
525 | error. | |
88145b29 | 526 | .SS Closing the fanotify file descriptor |
be8ba5d8 MK |
527 | .PP |
528 | When all file descriptors referring to the fanotify notification group are | |
529 | closed, the fanotify group is released and its resources | |
530 | are freed for reuse by the kernel. | |
531 | Upon | |
532 | .BR close (2), | |
533 | outstanding permission events will be set to allowed. | |
c00ff2dc | 534 | .SS /proc/[pid]/fdinfo |
597aaea2 | 535 | The file |
3d4433fe | 536 | .I /proc/[pid]/fdinfo/[fd] |
597aaea2 HS |
537 | contains information about fanotify marks for file descriptor |
538 | .I fd | |
539 | of process | |
540 | .IR pid . | |
75f8598a MK |
541 | See |
542 | .BR proc (5) | |
597aaea2 HS |
543 | for details. |
544 | .SH ERRORS | |
545 | In addition to the usual errors for | |
546 | .BR read (2), | |
1b24e2ee MK |
547 | the following errors can occur when reading from the |
548 | fanotify file descriptor: | |
597aaea2 HS |
549 | .TP |
550 | .B EINVAL | |
4a57583f | 551 | The buffer is too small to hold the event. |
597aaea2 HS |
552 | .TP |
553 | .B EMFILE | |
554 | The per-process limit on the number of open files has been reached. | |
555 | See the description of | |
556 | .B RLIMIT_NOFILE | |
557 | in | |
558 | .BR getrlimit (2). | |
559 | .TP | |
560 | .B ENFILE | |
e258766b | 561 | The system-wide limit on the total number of open files has been reached. |
597aaea2 | 562 | See |
fa6d3b26 | 563 | .I /proc/sys/fs/file\-max |
597aaea2 HS |
564 | in |
565 | .BR proc (5). | |
566 | .TP | |
567 | .B ETXTBSY | |
597aaea2 | 568 | This error is returned by |
68bcc008 | 569 | .BR read (2) |
597aaea2 HS |
570 | if |
571 | .B O_RDWR | |
572 | or | |
573 | .B O_WRONLY | |
574 | was specified in the | |
575 | .I event_f_flags | |
576 | argument when calling | |
577 | .BR fanotify_init (2) | |
68bcc008 | 578 | and an event occurred for a monitored file that is currently being executed. |
597aaea2 HS |
579 | .PP |
580 | In addition to the usual errors for | |
581 | .BR write (2), | |
582 | the following errors can occur when writing to the fanotify file descriptor: | |
583 | .TP | |
584 | .B EINVAL | |
1b24e2ee MK |
585 | Fanotify access permissions are not enabled in the kernel configuration |
586 | or the value of | |
597aaea2 HS |
587 | .I response |
588 | in the response structure is not valid. | |
589 | .TP | |
590 | .B ENOENT | |
591 | The file descriptor | |
592 | .I fd | |
593 | in the response structure is not valid. | |
33022419 MK |
594 | This may occur when a response for the permission event has already been |
595 | written. | |
597aaea2 HS |
596 | .SH VERSIONS |
597 | The fanotify API was introduced in version 2.6.36 of the Linux kernel and | |
598 | enabled in version 2.6.37. | |
599 | Fdinfo support was added in version 3.8. | |
d282bb24 | 600 | .SH CONFORMING TO |
597aaea2 HS |
601 | The fanotify API is Linux-specific. |
602 | .SH NOTES | |
603 | The fanotify API is available only if the kernel was built with the | |
604 | .B CONFIG_FANOTIFY | |
605 | configuration option enabled. | |
606 | In addition, fanotify permission handling is available only if the | |
607 | .B CONFIG_FANOTIFY_ACCESS_PERMISSIONS | |
608 | configuration option is enabled. | |
609 | .SS Limitations and caveats | |
610 | Fanotify reports only events that a user-space program triggers through the | |
611 | filesystem API. | |
1b24e2ee MK |
612 | As a result, |
613 | it does not catch remote events that occur on network filesystems. | |
597aaea2 HS |
614 | .PP |
615 | The fanotify API does not report file accesses and modifications that | |
616 | may occur because of | |
617 | .BR mmap (2), | |
618 | .BR msync (2), | |
619 | and | |
620 | .BR munmap (2). | |
621 | .PP | |
622 | Events for directories are created only if the directory itself is opened, | |
623 | read, and closed. | |
624 | Adding, removing, or changing children of a marked directory does not create | |
625 | events for the monitored directory itself. | |
626 | .PP | |
1b24e2ee MK |
627 | Fanotify monitoring of directories is not recursive: |
628 | to monitor subdirectories under a directory, | |
629 | additional marks must be created. | |
3d1ee497 | 630 | (But note that the fanotify API provides no way of detecting when a |
1b24e2ee MK |
631 | subdirectory has been created under a marked directory, |
632 | which makes recursive monitoring difficult.) | |
597aaea2 | 633 | Monitoring mounts offers the capability to monitor a whole directory tree. |
b2f8214d AG |
634 | Monitoring filesystems offers the capability to monitor changes made from |
635 | any mount of a filesystem instance. | |
597aaea2 HS |
636 | .PP |
637 | The event queue can overflow. | |
638 | In this case, events are lost. | |
639 | .SH BUGS | |
707914e9 MK |
640 | Before Linux 3.19, |
641 | .BR fallocate (2) | |
642 | did not generate fanotify events. | |
643 | Since Linux 3.19, | |
644 | .\" commit 820c12d5d6c0890bc93dd63893924a13041fdc35 | |
645 | calls to | |
646 | .BR fallocate (2) | |
647 | generate | |
648 | .B FAN_MODIFY | |
649 | events. | |
a721e8b2 | 650 | .PP |
d5b26a69 | 651 | As of Linux 3.17, |
1aa556ab | 652 | the following bugs exist: |
597aaea2 | 653 | .IP * 3 |
c5a00024 | 654 | On Linux, a filesystem object may be accessible through multiple paths, |
8e38f6d3 | 655 | for example, a part of a filesystem may be remounted using the |
c5a00024 MK |
656 | .IR \-\-bind |
657 | option of | |
658 | .BR mount (8). | |
659 | A listener that marked a mount will be notified only of events that were | |
660 | triggered for a filesystem object using the same mount. | |
a4b394f2 HS |
661 | Any other event will pass unnoticed. |
662 | .IP * | |
bea08fec | 663 | .\" FIXME . A patch was proposed. |
1b24e2ee MK |
664 | When an event is generated, |
665 | no check is made to see whether the user ID of the | |
666 | receiving process has authorization to read or write the file | |
667 | before passing a file descriptor for that file. | |
597aaea2 HS |
668 | This poses a security risk, when the |
669 | .B CAP_SYS_ADMIN | |
670 | capability is set for programs executed by unprivileged users. | |
f96adfdc HS |
671 | .IP * |
672 | If a call to | |
1c612526 | 673 | .BR read (2) |
e1001916 MK |
674 | processes multiple events from the fanotify queue and an error occurs, |
675 | the return value will be the total length of the events successfully | |
676 | copied to the user-space buffer before the error occurred. | |
677 | The return value will not be \-1, and | |
f96adfdc HS |
678 | .I errno |
679 | will not be set. | |
e1001916 | 680 | Thus, the reading application has no way to detect the error. |
597aaea2 | 681 | .SH EXAMPLE |
0a4db6dc | 682 | The two example programs below demonstrate the usage of the fanotify API. |
3051b98c MK |
683 | .SS Example program: fanotify_example.c |
684 | The first program is an example of fanotify being | |
0a4db6dc MB |
685 | used with its event object information passed in the form of a file |
686 | descriptor. | |
3051b98c MK |
687 | The program marks the mount point passed as a command-line argument and |
688 | waits for events of type | |
6684e3e4 | 689 | .B FAN_OPEN_PERM |
597aaea2 HS |
690 | and |
691 | .BR FAN_CLOSE_WRITE . | |
692 | When a permission event occurs, a | |
693 | .B FAN_ALLOW | |
694 | response is given. | |
695 | .PP | |
3051b98c MK |
696 | The following shell session shows an example of |
697 | running this program. | |
0a4db6dc | 698 | This session involved editing the file |
597aaea2 HS |
699 | .IR /home/user/temp/notes . |
700 | Before the file was opened, a | |
701 | .B FAN_OPEN_PERM | |
702 | event occurred. | |
703 | After the file was closed, a | |
704 | .B FAN_CLOSE_WRITE | |
705 | event occurred. | |
706 | Execution of the program ends when the user presses the ENTER key. | |
0a4db6dc | 707 | .PP |
597aaea2 | 708 | .in +4n |
b8302363 | 709 | .EX |
26f6196a | 710 | # \fB./fanotify_example /home\fP |
597aaea2 HS |
711 | Press enter key to terminate. |
712 | Listening for events. | |
713 | FAN_OPEN_PERM: File /home/user/temp/notes | |
714 | FAN_CLOSE_WRITE: File /home/user/temp/notes | |
715 | ||
716 | Listening for events stopped. | |
b8302363 | 717 | .EE |
3051b98c | 718 | .in |
0a4db6dc | 719 | .EE |
597aaea2 | 720 | .in |
0a4db6dc | 721 | .SS Program source: fanotify_example.c |
c7885256 | 722 | \& |
e7d0bb47 | 723 | .EX |
616fce49 | 724 | #define _GNU_SOURCE /* Needed to get O_LARGEFILE definition */ |
597aaea2 HS |
725 | #include <errno.h> |
726 | #include <fcntl.h> | |
727 | #include <limits.h> | |
728 | #include <poll.h> | |
729 | #include <stdio.h> | |
730 | #include <stdlib.h> | |
731 | #include <sys/fanotify.h> | |
732 | #include <unistd.h> | |
733 | ||
5ff63f51 | 734 | /* Read all available fanotify events from the file descriptor \(aqfd\(aq */ |
597aaea2 | 735 | |
815df19b | 736 | static void |
597aaea2 HS |
737 | handle_events(int fd) |
738 | { | |
739 | const struct fanotify_event_metadata *metadata; | |
864eccb9 | 740 | struct fanotify_event_metadata buf[200]; |
597aaea2 HS |
741 | ssize_t len; |
742 | char path[PATH_MAX]; | |
743 | ssize_t path_len; | |
744 | char procfd_path[PATH_MAX]; | |
745 | struct fanotify_response response; | |
746 | ||
f7767949 | 747 | /* Loop while events can be read from fanotify file descriptor */ |
597aaea2 | 748 | |
7877c846 | 749 | for (;;) { |
597aaea2 | 750 | |
f7767949 | 751 | /* Read some events */ |
597aaea2 HS |
752 | |
753 | len = read(fd, (void *) &buf, sizeof(buf)); | |
754 | if (len == \-1 && errno != EAGAIN) { | |
755 | perror("read"); | |
756 | exit(EXIT_FAILURE); | |
757 | } | |
758 | ||
f7767949 | 759 | /* Check if end of available data reached */ |
597aaea2 HS |
760 | |
761 | if (len <= 0) | |
762 | break; | |
763 | ||
f7767949 | 764 | /* Point to the first event in the buffer */ |
597aaea2 | 765 | |
864eccb9 | 766 | metadata = buf; |
597aaea2 | 767 | |
f7767949 | 768 | /* Loop over all events in the buffer */ |
597aaea2 HS |
769 | |
770 | while (FAN_EVENT_OK(metadata, len)) { | |
771 | ||
f7767949 | 772 | /* Check that run\-time and compile\-time structures match */ |
597aaea2 HS |
773 | |
774 | if (metadata\->vers != FANOTIFY_METADATA_VERSION) { | |
775 | fprintf(stderr, | |
d1a71985 | 776 | "Mismatch of fanotify metadata version.\en"); |
597aaea2 HS |
777 | exit(EXIT_FAILURE); |
778 | } | |
779 | ||
bfff73cb MK |
780 | /* metadata\->fd contains either FAN_NOFD, indicating a |
781 | queue overflow, or a file descriptor (a nonnegative | |
782 | integer). Here, we simply ignore queue overflow. */ | |
0554d3f7 | 783 | |
597aaea2 HS |
784 | if (metadata\->fd >= 0) { |
785 | ||
f7767949 | 786 | /* Handle open permission event */ |
597aaea2 HS |
787 | |
788 | if (metadata\->mask & FAN_OPEN_PERM) { | |
789 | printf("FAN_OPEN_PERM: "); | |
790 | ||
f7767949 | 791 | /* Allow file to be opened */ |
597aaea2 HS |
792 | |
793 | response.fd = metadata\->fd; | |
794 | response.response = FAN_ALLOW; | |
f7767949 | 795 | write(fd, &response, |
864eccb9 | 796 | sizeof(struct fanotify_response)); |
597aaea2 HS |
797 | } |
798 | ||
f7767949 | 799 | /* Handle closing of writable file event */ |
597aaea2 | 800 | |
f7767949 | 801 | if (metadata\->mask & FAN_CLOSE_WRITE) |
597aaea2 | 802 | printf("FAN_CLOSE_WRITE: "); |
597aaea2 | 803 | |
b34cbc45 | 804 | /* Retrieve and print pathname of the accessed file */ |
597aaea2 HS |
805 | |
806 | snprintf(procfd_path, sizeof(procfd_path), | |
807 | "/proc/self/fd/%d", metadata\->fd); | |
808 | path_len = readlink(procfd_path, path, | |
809 | sizeof(path) \- 1); | |
810 | if (path_len == \-1) { | |
811 | perror("readlink"); | |
812 | exit(EXIT_FAILURE); | |
813 | } | |
814 | ||
5ff63f51 | 815 | path[path_len] = \(aq\e0\(aq; |
d1a71985 | 816 | printf("File %s\en", path); |
597aaea2 | 817 | |
f7767949 | 818 | /* Close the file descriptor of the event */ |
597aaea2 HS |
819 | |
820 | close(metadata\->fd); | |
597aaea2 HS |
821 | } |
822 | ||
48fd9fe0 | 823 | /* Advance to next event */ |
597aaea2 HS |
824 | |
825 | metadata = FAN_EVENT_NEXT(metadata, len); | |
826 | } | |
827 | } | |
828 | } | |
829 | ||
830 | int | |
831 | main(int argc, char *argv[]) | |
832 | { | |
833 | char buf; | |
834 | int fd, poll_num; | |
835 | nfds_t nfds; | |
836 | struct pollfd fds[2]; | |
837 | ||
f7767949 | 838 | /* Check mount point is supplied */ |
597aaea2 HS |
839 | |
840 | if (argc != 2) { | |
d1a71985 | 841 | fprintf(stderr, "Usage: %s MOUNT\en", argv[0]); |
597aaea2 HS |
842 | exit(EXIT_FAILURE); |
843 | } | |
844 | ||
d1a71985 | 845 | printf("Press enter key to terminate.\en"); |
597aaea2 | 846 | |
f7767949 | 847 | /* Create the file descriptor for accessing the fanotify API */ |
597aaea2 HS |
848 | |
849 | fd = fanotify_init(FAN_CLOEXEC | FAN_CLASS_CONTENT | FAN_NONBLOCK, | |
850 | O_RDONLY | O_LARGEFILE); | |
851 | if (fd == \-1) { | |
852 | perror("fanotify_init"); | |
853 | exit(EXIT_FAILURE); | |
854 | } | |
855 | ||
f7767949 | 856 | /* Mark the mount for: |
597aaea2 | 857 | \- permission events before opening files |
f7767949 MK |
858 | \- notification events after closing a write\-enabled |
859 | file descriptor */ | |
597aaea2 HS |
860 | |
861 | if (fanotify_mark(fd, FAN_MARK_ADD | FAN_MARK_MOUNT, | |
943c52b7 | 862 | FAN_OPEN_PERM | FAN_CLOSE_WRITE, AT_FDCWD, |
597aaea2 HS |
863 | argv[1]) == \-1) { |
864 | perror("fanotify_mark"); | |
597aaea2 HS |
865 | exit(EXIT_FAILURE); |
866 | } | |
867 | ||
f7767949 | 868 | /* Prepare for polling */ |
597aaea2 HS |
869 | |
870 | nfds = 2; | |
871 | ||
f7767949 | 872 | /* Console input */ |
597aaea2 HS |
873 | |
874 | fds[0].fd = STDIN_FILENO; | |
875 | fds[0].events = POLLIN; | |
876 | ||
f7767949 | 877 | /* Fanotify input */ |
597aaea2 HS |
878 | |
879 | fds[1].fd = fd; | |
880 | fds[1].events = POLLIN; | |
881 | ||
f7767949 | 882 | /* This is the loop to wait for incoming events */ |
597aaea2 | 883 | |
d1a71985 | 884 | printf("Listening for events.\en"); |
370359a7 | 885 | |
597aaea2 HS |
886 | while (1) { |
887 | poll_num = poll(fds, nfds, \-1); | |
888 | if (poll_num == \-1) { | |
e1ca5880 MK |
889 | if (errno == EINTR) /* Interrupted by a signal */ |
890 | continue; /* Restart poll() */ | |
891 | ||
892 | perror("poll"); /* Unexpected error */ | |
597aaea2 HS |
893 | exit(EXIT_FAILURE); |
894 | } | |
370359a7 | 895 | |
597aaea2 HS |
896 | if (poll_num > 0) { |
897 | if (fds[0].revents & POLLIN) { | |
898 | ||
f7767949 | 899 | /* Console input is available: empty stdin and quit */ |
597aaea2 | 900 | |
5ff63f51 | 901 | while (read(STDIN_FILENO, &buf, 1) > 0 && buf != \(aq\en\(aq) |
597aaea2 HS |
902 | continue; |
903 | break; | |
904 | } | |
370359a7 | 905 | |
597aaea2 HS |
906 | if (fds[1].revents & POLLIN) { |
907 | ||
f7767949 | 908 | /* Fanotify events are available */ |
597aaea2 HS |
909 | |
910 | handle_events(fd); | |
911 | } | |
912 | } | |
913 | } | |
914 | ||
d1a71985 | 915 | printf("Listening for events stopped.\en"); |
f7767949 | 916 | exit(EXIT_SUCCESS); |
597aaea2 | 917 | } |
e7d0bb47 | 918 | .EE |
3051b98c MK |
919 | .\" |
920 | .SS Example program: fanotify_fid.c | |
921 | The second program is an example of fanotify being used with | |
922 | .B FAN_REPORT_FID | |
923 | enabled. | |
794b5143 | 924 | The program marks the filesystem object that is passed as |
3051b98c MK |
925 | a command-line argument |
926 | and waits until an event of type | |
927 | .B FAN_CREATE | |
928 | has occurred. | |
794b5143 MK |
929 | The event mask indicates which type of filesystem object\(emeither |
930 | a file or a directory\(emwas created". | |
3051b98c MK |
931 | Once all events have been read from the buffer and processed accordingly, |
932 | the program simply terminates. | |
933 | .PP | |
934 | The following shell sessions show two different invocations of | |
935 | this program, with different actions performed on a watched object. | |
936 | .PP | |
937 | The first session shows a mark being placed on | |
938 | .IR /home/user . | |
939 | This is followed by the creation of a regular file, | |
940 | .IR /home/user/testfile.txt . | |
941 | This results in a | |
942 | .B FAN_CREATE | |
943 | event being created and reported against the file's parent watched | |
944 | directory object. | |
945 | Program execution ends once all events captured within the buffer have | |
946 | been processed. | |
947 | Program execution ends once all events captured within the buffer are | |
948 | processed. | |
949 | .PP | |
950 | .in +4n | |
951 | .EX | |
952 | # \fB./fanotify_fid /home/user\fP | |
953 | Listening for events. | |
954 | FAN_CREATE (file created): Directory /home/user has been modified. | |
955 | All events processed successfully. Program exiting. | |
956 | ||
957 | $ \fBtouch /home/user/testing\fP # In another terminal | |
958 | .EE | |
959 | .in | |
960 | .PP | |
961 | The second session shows a mark being placed on | |
962 | .IR /home/user . | |
963 | This is followed by the creation of a directory, | |
964 | .IR /home/user/testdir . | |
965 | This specific action results in the program producing a | |
966 | .B FAN_CREATE | |
967 | and | |
968 | .B FAN_ONDIR | |
969 | event. | |
970 | .PP | |
971 | .in +4n | |
972 | .EX | |
973 | # \fB./fanotify_fid /home/user\fP | |
974 | Listening for events. | |
975 | FAN_CREATE | FAN_ONDIR (subdirectory created): | |
976 | Directory /home/user has been modified. | |
977 | All events processed successfully. Program exiting. | |
978 | ||
979 | $ \fBmkdir \-p /home/user/testing\fP # In another terminal | |
980 | .EE | |
0a4db6dc MB |
981 | .in |
982 | .SS Program source: fanotify_fid.c | |
983 | \& | |
984 | .EX | |
985 | #define _GNU_SOURCE | |
986 | #include <errno.h> | |
987 | #include <fcntl.h> | |
988 | #include <limits.h> | |
989 | #include <stdio.h> | |
990 | #include <stdlib.h> | |
991 | #include <sys/types.h> | |
992 | #include <sys/stat.h> | |
993 | #include <sys/fanotify.h> | |
994 | #include <unistd.h> | |
995 | ||
996 | #define BUF_SIZE 256 | |
997 | ||
6f10bd32 MK |
998 | int |
999 | main(int argc, char **argv) | |
0a4db6dc MB |
1000 | { |
1001 | int fd, ret, event_fd; | |
1002 | ssize_t len, path_len; | |
1003 | char path[PATH_MAX]; | |
1004 | char procfd_path[PATH_MAX]; | |
1005 | char events_buf[BUF_SIZE]; | |
0a4db6dc MB |
1006 | struct file_handle *file_handle; |
1007 | struct fanotify_event_metadata *metadata; | |
1008 | struct fanotify_event_info_fid *fid; | |
1009 | ||
1010 | if (argc != 2) { | |
5ff63f51 | 1011 | fprintf(stderr, "Invalid number of command line arguments.\e\n"); |
0a4db6dc MB |
1012 | exit(EXIT_FAILURE); |
1013 | } | |
1014 | ||
1015 | /* Create an fanotify file descriptor with FAN_REPORT_FID as a flag | |
87d12b1b MK |
1016 | so that program can receive fid events. */ |
1017 | ||
0a4db6dc | 1018 | fd = fanotify_init(FAN_CLASS_NOTIF | FAN_REPORT_FID, 0); |
5ff63f51 | 1019 | if (fd == \-1) { |
0a4db6dc MB |
1020 | perror("fanotify_init"); |
1021 | exit(EXIT_FAILURE); | |
1022 | } | |
1023 | ||
1024 | /* Place a mark on the filesystem object supplied in argv[1]. */ | |
87d12b1b | 1025 | |
0a4db6dc MB |
1026 | ret = fanotify_mark(fd, FAN_MARK_ADD | FAN_MARK_ONLYDIR, |
1027 | FAN_CREATE | FAN_ONDIR, | |
1028 | AT_FDCWD, argv[1]); | |
5ff63f51 | 1029 | if (ret == \-1) { |
0a4db6dc MB |
1030 | perror("fanotify_mark"); |
1031 | exit(EXIT_FAILURE); | |
1032 | } | |
1033 | ||
5ff63f51 | 1034 | printf("Listening for events.\e\n"); |
0a4db6dc MB |
1035 | |
1036 | /* Read events from the event queue into a buffer */ | |
87d12b1b | 1037 | |
0a4db6dc | 1038 | len = read(fd, (void *) &events_buf, sizeof(events_buf)); |
5ff63f51 | 1039 | if (len == \-1 && errno != EAGAIN) { |
0a4db6dc MB |
1040 | perror("read"); |
1041 | exit(EXIT_FAILURE); | |
1042 | } | |
1043 | ||
1044 | /* Process all events within the buffer */ | |
87d12b1b | 1045 | |
0a4db6dc MB |
1046 | for (metadata = (struct fanotify_event_metadata *) events_buf; |
1047 | FAN_EVENT_OK(metadata, len); | |
1048 | metadata = FAN_EVENT_NEXT(metadata, len)) { | |
1049 | fid = (struct fanotify_event_info_fid *) (metadata + 1); | |
1050 | file_handle = (struct file_handle *) fid->handle; | |
1051 | ||
1052 | /* Ensure that the event info is of the correct type */ | |
87d12b1b | 1053 | |
0a4db6dc | 1054 | if (fid->hdr.info_type != FAN_EVENT_INFO_TYPE_FID) { |
5ff63f51 | 1055 | fprintf(stderr, "Received unexpected event info type.\e\n"); |
0a4db6dc MB |
1056 | exit(EXIT_FAILURE); |
1057 | } | |
1058 | ||
1059 | if (metadata->mask == FAN_CREATE) | |
525b88e1 | 1060 | printf("FAN_CREATE (file created):"); |
0a4db6dc MB |
1061 | |
1062 | if (metadata->mask == FAN_CREATE | FAN_ONDIR) | |
525b88e1 | 1063 | printf("FAN_CREATE | FAN_ONDIR (subdirectory created):"); |
0a4db6dc MB |
1064 | |
1065 | /* metadata->fd is set to FAN_NOFD when FAN_REPORT_FID is enabled. | |
87d12b1b | 1066 | To obtain a file descriptor for the file object corresponding to |
5ff63f51 | 1067 | an event you can use the struct file_handle that\(aqs provided |
87d12b1b | 1068 | within the fanotify_event_info_fid in conjunction with the |
c6624006 | 1069 | open_by_handle_at(2) system call. A check for ESTALE is done |
794b5143 MK |
1070 | to accommodate for the situation where the file handle for the |
1071 | object was deleted prior to this system call. */ | |
87d12b1b | 1072 | |
0a4db6dc | 1073 | event_fd = open_by_handle_at(AT_FDCWD, file_handle, O_RDONLY); |
2d26ddfa MK |
1074 | if (ret == \-1) { |
1075 | if (errno == ESTALE) { | |
1076 | printf("File handle is no longer valid. " | |
1077 | "File has been deleted\e\n"); | |
1078 | continue; | |
1079 | } else { | |
1080 | perror("open_by_handle_at"); | |
1081 | exit(EXIT_FAILURE); | |
1082 | } | |
0a4db6dc MB |
1083 | } |
1084 | ||
6f10bd32 MK |
1085 | snprintf(procfd_path, sizeof(procfd_path), "/proc/self/fd/%d", |
1086 | event_fd); | |
0a4db6dc | 1087 | |
817c8240 | 1088 | /* Retrieve and print the path of the modified dentry */ |
87d12b1b | 1089 | |
5ff63f51 MK |
1090 | path_len = readlink(procfd_path, path, sizeof(path) \- 1); |
1091 | if (path_len == \-1) { | |
0a4db6dc MB |
1092 | perror("readlink"); |
1093 | exit(EXIT_FAILURE); | |
1094 | } | |
1095 | ||
5ff63f51 | 1096 | path[path_len] = \(aq\e\0\(aq; |
525b88e1 | 1097 | printf("\etDirectory \(aq%s\(aq has been modified.\e\n", path); |
0a4db6dc MB |
1098 | |
1099 | /* Close associated file descriptor for this event */ | |
5ff63f51 | 1100 | |
0a4db6dc MB |
1101 | close(event_fd); |
1102 | } | |
1103 | ||
5ff63f51 | 1104 | printf("All events processed successfully. Program exiting.\e\n"); |
0a4db6dc MB |
1105 | exit(EXIT_SUCCESS); |
1106 | } | |
1107 | .EE | |
d282bb24 | 1108 | .SH SEE ALSO |
597aaea2 HS |
1109 | .ad l |
1110 | .BR fanotify_init (2), | |
1111 | .BR fanotify_mark (2), | |
1112 | .BR inotify (7) |