Provided by: libsystemd-dev_245.4-4ubuntu3.24_amd64 
NAME
sd_event_add_inotify, sd_event_source_get_inotify_mask, sd_event_inotify_handler_t - Add
an "inotify" file system inode event source to an event loop
SYNOPSIS
#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_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 specifie 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.
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.
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.
EXAMPLES
Example 1. A simple program that uses inotify to monitor one or two directories
#include <stdio.h>
#include <string.h>
#include <sys/inotify.h>
#include <systemd/sd-event.h>
#define _cleanup_(f) __attribute__((cleanup(f)))
static int inotify_handler(sd_event_source *source,
const struct inotify_event *event,
void *userdata) {
const char *desc = NULL;
sd_event_source_get_description(source, &desc);
if (event->mask & IN_Q_OVERFLOW)
printf("inotify-handler <%s>: overflow\n", desc);
else if (event->mask & IN_CREATE)
printf("inotify-handler <%s>: create on %s\n", desc, event->name);
else if (event->mask & IN_DELETE)
printf("inotify-handler <%s>: delete on %s\n", desc, event->name);
else if (event->mask & IN_MOVED_TO)
printf("inotify-handler <%s>: moved-to on %s\n", desc, event->name);
/* Terminate the program if an "exit" file appears */
if ((event->mask & (IN_CREATE|IN_MOVED_TO)) &&
strcmp(event->name, "exit") == 0)
sd_event_exit(sd_event_source_get_event(source), 0);
return 1;
}
int main(int argc, char **argv) {
_cleanup_(sd_event_unrefp) sd_event *event = NULL;
_cleanup_(sd_event_source_unrefp) sd_event_source *source1 = NULL, *source2 = NULL;
const char *path1 = argc > 1 ? argv[1] : "/tmp";
const char *path2 = argc > 2 ? argv[2] : NULL;
/* Note: failure handling is omitted for brevity */
sd_event_default(&event);
sd_event_add_inotify(event, &source1, path1,
IN_CREATE | IN_DELETE | IN_MODIFY | IN_MOVED_TO,
inotify_handler, NULL);
if (path2)
sd_event_add_inotify(event, &source2, path2,
IN_CREATE | IN_DELETE | IN_MODIFY | IN_MOVED_TO,
inotify_handler, NULL);
sd_event_loop(event);
return 0;
}
NOTES
These APIs are implemented as a shared library, which can be compiled and linked to with
the libsystemd pkg-config(1) file.
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)