x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_EVENT_ADD_INOTIFY(3) sd_event_add_inotify SD_EVENT_ADD_INOTIFY(3)
NAME
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
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_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 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.
The handler must reference a function to call when the inode changes or
NULL. 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 handler may return negative to signal an error (see
below), other return values are ignored. If handler is NULL, a default
handler that calls sd_event_exit(3) will be used.
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, library or
module instance.
-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
Example 1. A simple program that uses inotify to monitor one or two
directories
/* SPDX-License-Identifier: MIT-0 */
#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
Functions described here are available as a shared library, which can
be compiled against and linked to with the libsystemd pkg-config(1)
file.
The code described here uses getenv(3), which is declared to be not
multi-thread-safe. This means that the code calling the functions
described here must not call setenv(3) from a parallel thread. It is
recommended to only do calls to setenv() from an early phase of the
program when no other threads have been started.
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)
systemd 254 SD_EVENT_ADD_INOTIFY(3)
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