добавить источник события inode файловой системы inotify в цикл событий (Add an "inotify" file system inode event source to an event loop)
Имя (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
Синопсис (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);
Описание (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.
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.
Возвращаемое значение (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.
Примеры (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;
}
Примечание (Note)
These APIs are implemented as a shared library, which can be
compiled and linked to with the libsystemd pkg-config(1) file.
Смотри также (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)
