|
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | EXAMPLES | NOTES | SEE ALSO | COLOPHON |
SD_EVENT_ADD_INOTIFY(3) sd_event_add_inotify SD_EVENT_ADD_INOTIFY(3)
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
#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);
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.
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.
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;
}
These APIs are implemented as a shared library, which can be compiled
and linked to with the libsystemd pkg-config(1) file.
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)
This page is part of the systemd (systemd system and service manager)
project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a bug
report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩. This
page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2020-08-13. (At that
time, the date of the most recent commit that was found in the repos‐
itory was 2020-08-11.) If you discover any rendering problems in
this HTML version of the page, or you believe there is a better or
more up-to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not part
of the original manual page), send a mail to man-pages@man7.org
systemd 246 SD_EVENT_ADD_INOTIFY(3)
Pages that refer to this page: 30-systemd-environment-d-generator(7) , systemd.index(7)