sd_event_add_inotify

systemd
sd_event_add_inotify 3
sd_event_add_inotify sd_event_add_inotify_fd sd_event_source_get_inotify_mask sd_event_inotify_handler_t Add an "inotify" file system inode event source to an event loop

    #include <systemd/sd-event.h>

    typedef struct sd_event_source sd_event_source;

typedef int (*`sd_event_inotify_handler_t`) sd_event_source *s const struct inotify_event *event void *userdata int `sd_event_add_inotify` sd_event *event sd_event_source **source const char *path uint32_t mask sd_event_inotify_handler_t handler void *userdata int `sd_event_add_inotify_fd` sd_event *event sd_event_source **source int fd uint32_t mask sd_event_inotify_handler_t handler void *userdata int `sd_event_source_get_inotify_mask` sd_event_source *source uint32_t *mask

## Description

`sd_event_add_inotify()` adds a new inotify 7 file system inode event source to an event loop. The event loop object is specified in the event parameter, the event source object is returned in the source parameter. The path parameter specifies the path of the file system inode to watch. The handler must reference a function to call when the inode changes. The handler function will be passed the userdata pointer, which may be chosen freely by the caller. The handler also receives a pointer to a struct inotify_event structure containing information about the inode event. The mask parameter specifies which types of inode events to watch specifically. It must contain an OR-ed combination of `IN_ACCESS`, `IN_ATTRIB`, `IN_CLOSE_WRITE`, … flags. See inotify 7 for further information.

`sd_event_add_inotify_fd()` is identical to `sd_event_add_inotify()`, except that it takes a file descriptor to an inode (possibly an `O_PATH` one, but any other will do too) instead of a path in the file system.

If multiple event sources are installed for the same inode the backing inotify watch descriptor is automatically shared. The mask parameter may contain any flag defined by the inotify API, with the exception of `IN_MASK_ADD`.

The handler is enabled continuously (`SD_EVENT_ON`), but this may be changed with sd_event_source_set_enabled 3. Alternatively, the `IN_ONESHOT` mask flag may be used to request `SD_EVENT_ONESHOT` mode. If the handler function returns a negative error code, it will be disabled after the invocation, even if the `SD_EVENT_ON` mode was requested before.

As a special limitation the priority of inotify event sources may only be altered (see sd_event_source_set_priority 3) in the time between creation of the event source object with `sd_event_add_inotify()` and the beginning of the next event loop iteration. Attempts of changing the priority any later will be refused. Consider freeing and allocating a new inotify event source to change the priority at that point.

To destroy an event source object use sd_event_source_unref 3, but note that the event source is only removed from the event loop when all references to the event source are dropped. To make sure an event source does not fire anymore, even when there's still a reference to it kept, consider disabling it with sd_event_source_set_enabled 3.

If the second parameter of `sd_event_add_inotify()` is passed as `NULL` no reference to the event source object is returned. In this case the event source is considered "floating", and will be destroyed implicitly when the event loop itself is destroyed.

If the handler parameter to `sd_event_add_inotify()` is `NULL`, and the event source fires, this will be considered a request to exit the event loop. In this case, the userdata parameter, cast to an integer, is passed as the exit code parameter to sd_event_exit 3.

`sd_event_source_get_inotify_mask()` retrieves the configured inotify watch mask of an event source created previously with `sd_event_add_inotify()`. It takes the event source object as the source parameter and a pointer to a uint32_t variable to return the mask in.

## Return Value

On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style error code.

### Errors

Returned errors may indicate the following problems:

`-ENOMEM`

  Not enough memory to allocate an object.

`-EINVAL`

  An invalid argument has been passed. This includes specifying a mask with `IN_MASK_ADD` set.

`-ESTALE`

  The event loop is already terminated.

`-ECHILD`

  The event loop has been created in a different process.

`-EDOM`

  The passed event source is not an inotify process event source.

`-EBADF`

  The passed file descriptor is not valid.

`-ENOSYS`

  `sd_event_add_inotify_fd()` was called without `/proc/` mounted.

## Examples

A simple program that uses inotify to monitor one or two directories

## See Also

systemd 1, sd-event 3, sd_event_new 3, sd_event_now 3, sd_event_add_io 3, sd_event_add_time 3, sd_event_add_signal 3, sd_event_add_defer 3, sd_event_add_child 3, sd_event_source_set_enabled 3, sd_event_source_set_priority 3, sd_event_source_set_userdata 3, sd_event_source_set_description 3, sd_event_source_set_floating 3, waitid 2