# man > inotify(7) [_inotify_(7)](https://www.chedong.com/phpMan.php/man/inotify/7/markdown) Miscellaneous Information Manual [_inotify_(7)](https://www.chedong.com/phpMan.php/man/inotify/7/markdown) ## NAME inotify - monitoring filesystem events ## DESCRIPTION The _inotify_ API provides a mechanism for monitoring filesystem events. Inotify can be used to monitor individual files, or to monitor directories. When a directory is monitored, ino‐ tify will return events for the directory itself, and for files inside the directory. The following system calls are used with this API: • [**inotify_init**(2)](https://www.chedong.com/phpMan.php/man/inotifyinit/2/markdown) creates an inotify instance and returns a file descriptor referring to the inotify instance. The more recent [**inotify_init1**(2)](https://www.chedong.com/phpMan.php/man/inotifyinit1/2/markdown) is like [**inotify_init**(2)](https://www.chedong.com/phpMan.php/man/inotifyinit/2/markdown), but has a _flags_ argument that provides access to some extra functionality. • [**inotify_add_watch**(2)](https://www.chedong.com/phpMan.php/man/inotifyaddwatch/2/markdown) manipulates the "watch list" associated with an inotify instance. Each item ("watch") in the watch list specifies the pathname of a file or directory, along with some set of events that the kernel should monitor for the file referred to by that pathname. [**inotify_add_watch**(2)](https://www.chedong.com/phpMan.php/man/inotifyaddwatch/2/markdown) either creates a new watch item, or modifies an existing watch. Each watch has a unique "watch descriptor", an integer returned by **ino‐** [**tify_add_watch**(2)](https://www.chedong.com/phpMan.php/man/tifyaddwatch/2/markdown) when the watch is created. • When events occur for monitored files and directories, those events are made available to the application as structured data that can be read from the inotify file descriptor using [**read**(2)](https://www.chedong.com/phpMan.php/man/read/2/markdown) (see below). • [**inotify_rm_watch**(2)](https://www.chedong.com/phpMan.php/man/inotifyrmwatch/2/markdown) removes an item from an inotify watch list. • When all file descriptors referring to an inotify instance have been closed (using [**close**(2)](https://www.chedong.com/phpMan.php/man/close/2/markdown)), the underlying object and its resources are freed for reuse by the kernel; all associated watches are automatically freed. With careful programming, an application can use inotify to efficiently monitor and cache the state of a set of filesystem objects. However, robust applications should allow for the fact that bugs in the monitoring logic or races of the kind described below may leave the cache inconsistent with the filesystem state. It is probably wise to do some consistency checking, and rebuild the cache when inconsistencies are detected. ### Reading events from an inotify file descriptor To determine what events have occurred, an application [**read**(2)](https://www.chedong.com/phpMan.php/man/read/2/markdown)s from the inotify file de‐ scriptor. If no events have so far occurred, then, assuming a blocking file descriptor, [**read**(2)](https://www.chedong.com/phpMan.php/man/read/2/markdown) will block until at least one event occurs (unless interrupted by a signal, in which case the call fails with the error **EINTR**; see [**signal**(7)](https://www.chedong.com/phpMan.php/man/signal/7/markdown)). Each successful [**read**(2)](https://www.chedong.com/phpMan.php/man/read/2/markdown) returns a buffer containing one or more of the following structures: struct inotify_event { int wd; /* Watch descriptor */ uint32_t mask; /* Mask describing event */ uint32_t cookie; /* Unique cookie associating related events (for [rename(2)](https://www.chedong.com/phpMan.php/man/rename/2/markdown)) */ uint32_t len; /* Size of _name_ field */ char name[]; /* Optional null-terminated name */ }; _wd_ identifies the watch for which this event occurs. It is one of the watch descriptors re‐ turned by a previous call to [**inotify_add_watch**(2)](https://www.chedong.com/phpMan.php/man/inotifyaddwatch/2/markdown). _mask_ contains bits that describe the event that occurred (see below). _cookie_ is a unique integer that connects related events. Currently, this is used only for rename events, and allows the resulting pair of **IN_MOVED_FROM **and **IN_MOVED_TO **events to be connected by the application. For all other event types, _cookie_ is set to 0. The _name_ field is present only when an event is returned for a file inside a watched direc‐ tory; it identifies the filename within the watched directory. This filename is null-termi‐ nated, and may include further null bytes ('\0') to align subsequent reads to a suitable ad‐ dress boundary. The _len_ field counts all of the bytes in _name_, including the null bytes; the length of each _inotify_event_ structure is thus _sizeof(struct_ _inotify_event)+len_. The behavior when the buffer given to [**read**(2)](https://www.chedong.com/phpMan.php/man/read/2/markdown) is too small to return information about the next event depends on the kernel version: before Linux 2.6.21, [**read**(2)](https://www.chedong.com/phpMan.php/man/read/2/markdown) returns 0; since Linux 2.6.21, [**read**(2)](https://www.chedong.com/phpMan.php/man/read/2/markdown) fails with the error **EINVAL**. Specifying a buffer of size sizeof(struct inotify_event) + NAME_MAX + 1 will be sufficient to read at least one event. ### inotify events The [**inotify_add_watch**(2)](https://www.chedong.com/phpMan.php/man/inotifyaddwatch/2/markdown) _mask_ argument and the _mask_ field of the _inotify_event_ structure re‐ turned when [**read**(2)](https://www.chedong.com/phpMan.php/man/read/2/markdown)ing an inotify file descriptor are both bit masks identifying inotify events. The following bits can be specified in _mask_ when calling [**inotify_add_watch**(2)](https://www.chedong.com/phpMan.php/man/inotifyaddwatch/2/markdown) and may be returned in the _mask_ field returned by [**read**(2)](https://www.chedong.com/phpMan.php/man/read/2/markdown): **IN_ACCESS **(+) File was accessed (e.g., [**read**(2)](https://www.chedong.com/phpMan.php/man/read/2/markdown), [**execve**(2)](https://www.chedong.com/phpMan.php/man/execve/2/markdown)). **IN_ATTRIB **(*) Metadata changed—for example, permissions (e.g., [**chmod**(2)](https://www.chedong.com/phpMan.php/man/chmod/2/markdown)), timestamps (e.g., **uti‐** [**mensat**(2)](https://www.chedong.com/phpMan.php/man/mensat/2/markdown)), extended attributes ([**setxattr**(2)](https://www.chedong.com/phpMan.php/man/setxattr/2/markdown)), link count (since Linux 2.6.25; e.g., for the target of [**link**(2)](https://www.chedong.com/phpMan.php/man/link/2/markdown) and for [**unlink**(2)](https://www.chedong.com/phpMan.php/man/unlink/2/markdown)), and user/group ID (e.g., [**chown**(2)](https://www.chedong.com/phpMan.php/man/chown/2/markdown)). **IN_CLOSE_WRITE **(+) File opened for writing was closed. **IN_CLOSE_NOWRITE **(*) File or directory not opened for writing was closed. **IN_CREATE **(+) File/directory created in watched directory (e.g., [**open**(2)](https://www.chedong.com/phpMan.php/man/open/2/markdown) **O_CREAT**, [**mkdir**(2)](https://www.chedong.com/phpMan.php/man/mkdir/2/markdown), [**link**(2)](https://www.chedong.com/phpMan.php/man/link/2/markdown), [**symlink**(2)](https://www.chedong.com/phpMan.php/man/symlink/2/markdown), [**bind**(2)](https://www.chedong.com/phpMan.php/man/bind/2/markdown) on a UNIX domain socket). **IN_DELETE **(+) File/directory deleted from watched directory. **IN_DELETE_SELF** Watched file/directory was itself deleted. (This event also occurs if an object is moved to another filesystem, since [**mv**(1)](https://www.chedong.com/phpMan.php/man/mv/1/markdown) in effect copies the file to the other filesystem and then deletes it from the original filesystem.) In addition, an **IN_IGNORED **event will subsequently be generated for the watch descriptor. **IN_MODIFY **(+) File was modified (e.g., [**write**(2)](https://www.chedong.com/phpMan.php/man/write/2/markdown), [**truncate**(2)](https://www.chedong.com/phpMan.php/man/truncate/2/markdown)). **IN_MOVE_SELF** Watched file/directory was itself moved. **IN_MOVED_FROM **(+) Generated for the directory containing the old filename when a file is renamed. **IN_MOVED_TO **(+) Generated for the directory containing the new filename when a file is renamed. **IN_OPEN **(*) File or directory was opened. Inotify monitoring is inode-based: when monitoring a file (but not when monitoring the direc‐ tory containing a file), an event can be generated for activity on any link to the file (in the same or a different directory). When monitoring a directory: • the events marked above with an asterisk (*) can occur both for the directory itself and for objects inside the directory; and • the events marked with a plus sign (+) occur only for objects inside the directory (not for the directory itself). _Note_: when monitoring a directory, events are not generated for the files inside the direc‐ tory when the events are performed via a pathname (i.e., a link) that lies outside the moni‐ tored directory. When events are generated for objects inside a watched directory, the _name_ field in the re‐ turned _inotify_event_ structure identifies the name of the file within the directory. The **IN_ALL_EVENTS **macro is defined as a bit mask of all of the above events. This macro can be used as the _mask_ argument when calling [**inotify_add_watch**(2)](https://www.chedong.com/phpMan.php/man/inotifyaddwatch/2/markdown). Two additional convenience macros are defined: **IN_MOVE** Equates to **IN_MOVED_FROM | IN_MOVED_TO**. **IN_CLOSE** Equates to **IN_CLOSE_WRITE | IN_CLOSE_NOWRITE**. The following further bits can be specified in _mask_ when calling [**inotify_add_watch**(2)](https://www.chedong.com/phpMan.php/man/inotifyaddwatch/2/markdown): **IN_DONT_FOLLOW **(since Linux 2.6.15) Don't dereference _pathname_ if it is a symbolic link. **IN_EXCL_UNLINK **(since Linux 2.6.36) By default, when watching events on the children of a directory, events are gener‐ ated for children even after they have been unlinked from the directory. This can result in large numbers of uninteresting events for some applications (e.g., if watching _/tmp_, in which many applications create temporary files whose names are immediately unlinked). Specifying **IN_EXCL_UNLINK **changes the default behavior, so that events are not generated for children after they have been unlinked from the watched directory. **IN_MASK_ADD** If a watch instance already exists for the filesystem object corresponding to _pathname_, add (OR) the events in _mask_ to the watch mask (instead of replacing the mask); the error **EINVAL **results if **IN_MASK_CREATE **is also specified. **IN_ONESHOT** Monitor the filesystem object corresponding to _pathname_ for one event, then remove from watch list. **IN_ONLYDIR **(since Linux 2.6.15) Watch _pathname_ only if it is a directory; the error **ENOTDIR **results if _pathname_ is not a directory. Using this flag provides an application with a race-free way of ensuring that the monitored object is a directory. **IN_MASK_CREATE **(since Linux 4.18) Watch _pathname_ only if it does not already have a watch associated with it; the error **EEXIST **results if _pathname_ is already being watched. Using this flag provides an application with a way of ensuring that new watches do not modify existing ones. This is useful because multiple paths may refer to the same inode, and multiple calls to [**inotify_add_watch**(2)](https://www.chedong.com/phpMan.php/man/inotifyaddwatch/2/markdown) without this flag may clob‐ ber existing watch masks. The following bits may be set in the _mask_ field returned by [**read**(2)](https://www.chedong.com/phpMan.php/man/read/2/markdown): **IN_IGNORED** Watch was removed explicitly ([**inotify_rm_watch**(2)](https://www.chedong.com/phpMan.php/man/inotifyrmwatch/2/markdown)) or automatically (file was deleted, or filesystem was unmounted). See also BUGS. **IN_ISDIR** Subject of this event is a directory. **IN_Q_OVERFLOW** Event queue overflowed (_wd_ is -1 for this event). **IN_UNMOUNT** Filesystem containing watched object was unmounted. In addition, an **IN_IGNORED** event will subsequently be generated for the watch descriptor. ### Examples Suppose an application is watching the directory _dir_ and the file _dir/myfile_ for all events. The examples below show some events that will be generated for these two objects. fd = open("dir/myfile", O_RDWR); Generates **IN_OPEN **events for both _dir_ and _dir/myfile_. read(fd, buf, count); Generates **IN_ACCESS **events for both _dir_ and _dir/myfile_. write(fd, buf, count); Generates **IN_MODIFY **events for both _dir_ and _dir/myfile_. fchmod(fd, mode); Generates **IN_ATTRIB **events for both _dir_ and _dir/myfile_. close(fd); Generates **IN_CLOSE_WRITE **events for both _dir_ and _dir/myfile_. Suppose an application is watching the directories _dir1_ and _dir2_, and the file _dir1/myfile_. The following examples show some events that may be generated. link("dir1/myfile", "dir2/new"); Generates an **IN_ATTRIB **event for _myfile_ and an **IN_CREATE **event for _dir2_. rename("dir1/myfile", "dir2/myfile"); Generates an **IN_MOVED_FROM **event for _dir1_, an **IN_MOVED_TO **event for _dir2_, and an **IN_MOVE_SELF **event for _myfile_. The **IN_MOVED_FROM **and **IN_MOVED_TO **events will have the same _cookie_ value. Suppose that _dir1/xx_ and _dir2/yy_ are (the only) links to the same file, and an application is watching _dir1_, _dir2_, _dir1/xx_, and _dir2/yy_. Executing the following calls in the order given below will generate the following events: unlink("dir2/yy"); Generates an **IN_ATTRIB **event for _xx_ (because its link count changes) and an **IN_DELETE **event for _dir2_. unlink("dir1/xx"); Generates **IN_ATTRIB**, **IN_DELETE_SELF**, and **IN_IGNORED **events for _xx_, and an **IN_DELETE **event for _dir1_. Suppose an application is watching the directory _dir_ and (the empty) directory _dir/subdir_. The following examples show some events that may be generated. mkdir("dir/new", mode); Generates an **IN_CREATE | IN_ISDIR **event for _dir_. rmdir("dir/subdir"); Generates **IN_DELETE_SELF **and **IN_IGNORED **events for _subdir_, and an **IN_DELETE |** **IN_ISDIR **event for _dir_. ### /proc interfaces The following interfaces can be used to limit the amount of kernel memory consumed by ino‐ tify: _/proc/sys/fs/inotify/max_queued_events_ The value in this file is used when an application calls [**inotify_init**(2)](https://www.chedong.com/phpMan.php/man/inotifyinit/2/markdown) to set an up‐ per limit on the number of events that can be queued to the corresponding inotify in‐ stance. Events in excess of this limit are dropped, but an **IN_Q_OVERFLOW **event is al‐ ways generated. _/proc/sys/fs/inotify/max_user_instances_ This specifies an upper limit on the number of inotify instances that can be created per real user ID. _/proc/sys/fs/inotify/max_user_watches_ This specifies an upper limit on the number of watches that can be created per real user ID. ## STANDARDS Linux. ## HISTORY Inotify was merged into Linux 2.6.13. The required library interfaces were added in glibc 2.4. (**IN_DONT_FOLLOW**, **IN_MASK_ADD**, and **IN_ONLYDIR **were added in glibc 2.5.) ## NOTES Inotify file descriptors can be monitored using [**select**(2)](https://www.chedong.com/phpMan.php/man/select/2/markdown), [**poll**(2)](https://www.chedong.com/phpMan.php/man/poll/2/markdown), and [**epoll**(7)](https://www.chedong.com/phpMan.php/man/epoll/7/markdown). When an event is available, the file descriptor indicates as readable. Since Linux 2.6.25, signal-driven I/O notification is available for inotify file descriptors; see the discussion of **F_SETFL **(for setting the **O_ASYNC **flag), **F_SETOWN**, and **F_SETSIG **in **fc‐** [**ntl**(2)](https://www.chedong.com/phpMan.php/man/ntl/2/markdown). The _siginfo_t_ structure (described in [**sigaction**(2)](https://www.chedong.com/phpMan.php/man/sigaction/2/markdown)) that is passed to the signal handler has the following fields set: _si_fd_ is set to the inotify file descriptor number; _si_signo_ is set to the signal number; _si_code_ is set to **POLL_IN**; and **POLLIN **is set in _si_band_. If successive output inotify events produced on the inotify file descriptor are identical (same _wd_, _mask_, _cookie_, and _name_), then they are coalesced into a single event if the older event has not yet been read (but see BUGS). This reduces the amount of kernel memory re‐ quired for the event queue, but also means that an application can't use inotify to reliably count file events. The events returned by reading from an inotify file descriptor form an ordered queue. Thus, for example, it is guaranteed that when renaming from one directory to another, events will be produced in the correct order on the inotify file descriptor. The set of watch descriptors that is being monitored via an inotify file descriptor can be viewed via the entry for the inotify file descriptor in the process's _/proc/_pid_/fdinfo_ direc‐ tory. See [**proc**(5)](https://www.chedong.com/phpMan.php/man/proc/5/markdown) for further details. The **FIONREAD [ioctl**(2)](https://www.chedong.com/phpMan.php/man/ioctl/2/markdown) returns the number of bytes available to read from an inotify file descriptor. ### Limitations and caveats The inotify API provides no information about the user or process that triggered the inotify event. In particular, there is no easy way for a process that is monitoring events via ino‐ tify to distinguish events that it triggers itself from those that are triggered by other processes. Inotify reports only events that a user-space program triggers through the filesystem API. As a result, it does not catch remote events that occur on network filesystems. (Applica‐ tions must fall back to polling the filesystem to catch such events.) Furthermore, various pseudo-filesystems such as _/proc_, _/sys_, and _/dev/pts_ are not monitorable with inotify. The inotify API does not report file accesses and modifications that may occur because of [**mmap**(2)](https://www.chedong.com/phpMan.php/man/mmap/2/markdown), [**msync**(2)](https://www.chedong.com/phpMan.php/man/msync/2/markdown), and [**munmap**(2)](https://www.chedong.com/phpMan.php/man/munmap/2/markdown). The inotify API identifies affected files by filename. However, by the time an application processes an inotify event, the filename may already have been deleted or renamed. The inotify API identifies events via watch descriptors. It is the application's responsi‐ bility to cache a mapping (if one is needed) between watch descriptors and pathnames. Be aware that directory renamings may affect multiple cached pathnames. Inotify monitoring of directories is not recursive: to monitor subdirectories under a direc‐ tory, additional watches must be created. This can take a significant amount time for large directory trees. If monitoring an entire directory subtree, and a new subdirectory is created in that tree or an existing directory is renamed into that tree, be aware that by the time you create a watch for the new subdirectory, new files (and subdirectories) may already exist inside the subdi‐ rectory. Therefore, you may want to scan the contents of the subdirectory immediately after adding the watch (and, if desired, recursively add watches for any subdirectories that it contains). Note that the event queue can overflow. In this case, events are lost. Robust applications should handle the possibility of lost events gracefully. For example, it may be necessary to rebuild part or all of the application cache. (One simple, but possibly expensive, approach is to close the inotify file descriptor, empty the cache, create a new inotify file descrip‐ tor, and then re-create watches and cache entries for the objects to be monitored.) If a filesystem is mounted on top of a monitored directory, no event is generated, and no events are generated for objects immediately under the new mount point. If the filesystem is subsequently unmounted, events will subsequently be generated for the directory and the ob‐ jects it contains. ### Dealing with rename() events As noted above, the **IN_MOVED_FROM **and **IN_MOVED_TO **event pair that is generated by [**rename**(2)](https://www.chedong.com/phpMan.php/man/rename/2/markdown) can be matched up via their shared cookie value. However, the task of matching has some challenges. These two events are usually consecutive in the event stream available when reading from the inotify file descriptor. However, this is not guaranteed. If multiple processes are trig‐ gering events for monitored objects, then (on rare occasions) an arbitrary number of other events may appear between the **IN_MOVED_FROM **and **IN_MOVED_TO **events. Furthermore, it is not guaranteed that the event pair is atomically inserted into the queue: there may be a brief interval where the **IN_MOVED_FROM **has appeared, but the **IN_MOVED_TO **has not. Matching up the **IN_MOVED_FROM **and **IN_MOVED_TO **event pair generated by [**rename**(2)](https://www.chedong.com/phpMan.php/man/rename/2/markdown) is thus in‐ herently racy. (Don't forget that if an object is renamed outside of a monitored directory, there may not even be an **IN_MOVED_TO **event.) Heuristic approaches (e.g., assume the events are always consecutive) can be used to ensure a match in most cases, but will inevitably miss some cases, causing the application to perceive the **IN_MOVED_FROM **and **IN_MOVED_TO **events as being unrelated. If watch descriptors are destroyed and re-created as a result, then those watch descriptors will be inconsistent with the watch descriptors in any pending events. (Re-creating the inotify file descriptor and rebuilding the cache may be useful to deal with this scenario.) Applications should also allow for the possibility that the **IN_MOVED_FROM **event was the last event that could fit in the buffer returned by the current call to [**read**(2)](https://www.chedong.com/phpMan.php/man/read/2/markdown), and the accompa‐ nying **IN_MOVED_TO **event might be fetched only on the next [**read**(2)](https://www.chedong.com/phpMan.php/man/read/2/markdown), which should be done with a (small) timeout to allow for the fact that insertion of the **IN_MOVED_FROM**+**IN_MOVED_TO **event pair is not atomic, and also the possibility that there may not be any **IN_MOVED_TO **event. ## BUGS Before Linux 3.19, [**fallocate**(2)](https://www.chedong.com/phpMan.php/man/fallocate/2/markdown) did not create any inotify events. Since Linux 3.19, calls to [**fallocate**(2)](https://www.chedong.com/phpMan.php/man/fallocate/2/markdown) generate **IN_MODIFY **events. Before Linux 2.6.16, the **IN_ONESHOT _**mask_ flag does not work. As originally designed and implemented, the **IN_ONESHOT **flag did not cause an **IN_IGNORED **event to be generated when the watch was dropped after one event. However, as an unintended effect of other changes, since Linux 2.6.36, an **IN_IGNORED **event is generated in this case. Before Linux 2.6.25, the kernel code that was intended to coalesce successive identical events (i.e., the two most recent events could potentially be coalesced if the older had not yet been read) instead checked if the most recent event could be coalesced with the _oldest_ unread event. When a watch descriptor is removed by calling [**inotify_rm_watch**(2)](https://www.chedong.com/phpMan.php/man/inotifyrmwatch/2/markdown) (or because a watch file is deleted or the filesystem that contains it is unmounted), any pending unread events for that watch descriptor remain available to read. As watch descriptors are subsequently allocated with [**inotify_add_watch**(2)](https://www.chedong.com/phpMan.php/man/inotifyaddwatch/2/markdown), the kernel cycles through the range of possible watch descriptors (1 to **INT_MAX**) incrementally. When allocating a free watch descriptor, no check is made to see whether that watch descriptor number has any pending unread events in the inotify queue. Thus, it can happen that a watch descriptor is reallocated even when pending unread events exist for a previous incarnation of that watch descriptor number, with the result that the application might then read those events and interpret them as belonging to the file associ‐ ated with the newly recycled watch descriptor. In practice, the likelihood of hitting this bug may be extremely low, since it requires that an application cycle through **INT_MAX **watch descriptors, release a watch descriptor while leaving unread events for that watch descriptor in the queue, and then recycle that watch descriptor. For this reason, and because there have been no reports of the bug occurring in real-world applications, as of Linux 3.15, no kernel changes have yet been made to eliminate this possible bug. ## EXAMPLES The following program demonstrates the usage of the inotify API. It marks the directories passed as a command-line arguments and waits for events of type **IN_OPEN**, **IN_CLOSE_NOWRITE**, and **IN_CLOSE_WRITE**. The following output was recorded while editing the file _/home/user/temp/foo_ and listing di‐ rectory _/tmp_. Before the file and the directory were opened, **IN_OPEN **events occurred. After the file was closed, an **IN_CLOSE_WRITE **event occurred. After the directory was closed, an **IN_CLOSE_NOWRITE **event occurred. Execution of the program ended when the user pressed the ENTER key. ### Example output $ **./a.out /tmp /home/user/temp** Press enter key to terminate. Listening for events. IN_OPEN: /home/user/temp/foo [file] IN_CLOSE_WRITE: /home/user/temp/foo [file] IN_OPEN: /tmp/ [directory] IN_CLOSE_NOWRITE: /tmp/ [directory] Listening for events stopped. ### Program source #include #include #include #include #include #include #include /* Read all available inotify events from the file descriptor 'fd'. wd is the table of watch descriptors for the directories in argv. argc is the length of wd and argv. argv is the list of watched directories. Entry 0 of wd and argv is unused. */ static void handle_events(int fd, int *wd, int argc, char* argv[]) { /* Some systems cannot read integer variables if they are not properly aligned. On other systems, incorrect alignment may decrease performance. Hence, the buffer used for reading from the inotify file descriptor should have the same alignment as struct inotify_event. */ char buf[4096] __attribute__ ((aligned(__alignof__(struct inotify_event)))); const struct inotify_event *event; ssize_t len; /* Loop while events can be read from inotify file descriptor. */ for (;;) { /* Read some events. */ len = read(fd, buf, sizeof(buf)); if (len == -1 && errno != EAGAIN) { perror("read"); exit(EXIT_FAILURE); } /* If the nonblocking read() found no events to read, then it returns -1 with errno set to EAGAIN. In that case, we exit the loop. */ if (len <= 0) break; /* Loop over all events in the buffer. */ for (char *ptr = buf; ptr < buf + len; ptr += sizeof(struct inotify_event) + event->len) { event = (const struct inotify_event *) ptr; /* Print event type. */ if (event->mask & IN_OPEN) printf("IN_OPEN: "); if (event->mask & IN_CLOSE_NOWRITE) printf("IN_CLOSE_NOWRITE: "); if (event->mask & IN_CLOSE_WRITE) printf("IN_CLOSE_WRITE: "); /* Print the name of the watched directory. */ for (size_t i = 1; i < argc; ++i) { if (wd[i] == event->wd) { printf("%s/", argv[i]); break; } } /* Print the name of the file. */ if (event->len) printf("%s", event->name); /* Print type of filesystem object. */ if (event->mask & IN_ISDIR) printf(" [directory]\n"); else printf(" [file]\n"); } } } int main(int argc, char* argv[]) { char buf; int fd, i, poll_num; int *wd; nfds_t nfds; struct pollfd fds[2]; if (argc < 2) { printf("Usage: %s PATH [PATH ...]\n", argv[0]); exit(EXIT_FAILURE); } printf("Press ENTER key to terminate.\n"); /* Create the file descriptor for accessing the inotify API. */ fd = inotify_init1(IN_NONBLOCK); if (fd == -1) { perror("inotify_init1"); exit(EXIT_FAILURE); } /* Allocate memory for watch descriptors. */ wd = calloc(argc, sizeof(int)); if (wd == NULL) { perror("calloc"); exit(EXIT_FAILURE); } /* Mark directories for events - file was opened - file was closed */ for (i = 1; i < argc; i++) { wd[i] = inotify_add_watch(fd, argv[i], IN_OPEN | IN_CLOSE); if (wd[i] == -1) { fprintf(stderr, "Cannot watch '%s': %s\n", argv[i], strerror(errno)); exit(EXIT_FAILURE); } } /* Prepare for polling. */ nfds = 2; fds[0].fd = STDIN_FILENO; /* Console input */ fds[0].events = POLLIN; fds[1].fd = fd; /* Inotify input */ fds[1].events = POLLIN; /* Wait for events and/or terminal input. */ printf("Listening for events.\n"); while (1) { poll_num = poll(fds, nfds, -1); if (poll_num == -1) { if (errno == EINTR) continue; perror("poll"); exit(EXIT_FAILURE); } if (poll_num > 0) { if (fds[0].revents & POLLIN) { /* Console input is available. Empty stdin and quit. */ while (read(STDIN_FILENO, &buf, 1) > 0 && buf != '\n') continue; break; } if (fds[1].revents & POLLIN) { /* Inotify events are available. */ handle_events(fd, wd, argc, argv); } } } printf("Listening for events stopped.\n"); /* Close inotify file descriptor. */ close(fd); free(wd); exit(EXIT_SUCCESS); } ## SEE ALSO [**inotifywait**(1)](https://www.chedong.com/phpMan.php/man/inotifywait/1/markdown), [**inotifywatch**(1)](https://www.chedong.com/phpMan.php/man/inotifywatch/1/markdown), [**inotify_add_watch**(2)](https://www.chedong.com/phpMan.php/man/inotifyaddwatch/2/markdown), [**inotify_init**(2)](https://www.chedong.com/phpMan.php/man/inotifyinit/2/markdown), [**inotify_init1**(2)](https://www.chedong.com/phpMan.php/man/inotifyinit1/2/markdown), **in‐** [**otify_rm_watch**(2)](https://www.chedong.com/phpMan.php/man/otifyrmwatch/2/markdown), [**read**(2)](https://www.chedong.com/phpMan.php/man/read/2/markdown), [**stat**(2)](https://www.chedong.com/phpMan.php/man/stat/2/markdown), [**fanotify**(7)](https://www.chedong.com/phpMan.php/man/fanotify/7/markdown) _Documentation/filesystems/inotify.txt_ in the Linux kernel source tree Linux man-pages 6.7 2023-10-31 [_inotify_(7)](https://www.chedong.com/phpMan.php/man/inotify/7/markdown)