|
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | NOTES | SEE ALSO | COLOPHON |
SD_EVENT_ADD_DEFER(3) sd_event_add_defer SD_EVENT_ADD_DEFER(3)
sd_event_add_defer, sd_event_add_post, sd_event_add_exit,
sd_event_handler_t - Add static event sources to an event loop
#include <systemd/sd-event.h>
typedef struct sd_event_source sd_event_source;
typedef int (*sd_event_handler_t)(sd_event_source *s,
void *userdata);
int sd_event_add_defer(sd_event *event, sd_event_source **source,
sd_event_handler_t handler, void *userdata);
int sd_event_add_post(sd_event *event, sd_event_source **source,
sd_event_handler_t handler, void *userdata);
int sd_event_add_exit(sd_event *event, sd_event_source **source,
sd_event_handler_t handler, void *userdata);
These three functions add new static event sources 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 event sources
are enabled statically and will "fire" when the event loop is run and
the conditions described below are met. The handler function will be
passed the userdata pointer, which may be chosen freely by the
caller.
sd_event_add_defer() adds a new event source that will be dispatched
instantly, before the event loop goes to sleep again and waits for
new events. By default, the handler will be called once
(SD_EVENT_ONESHOT). Note that if the event source is set to
SD_EVENT_ON the event loop will never go to sleep again, but
continuously call the handler, possibly interleaved with other event
sources.
sd_event_add_post() adds a new event source that is run before the
event loop will sleep and wait for new events, but only after at
least one other non-post event source was dispatched. By default, the
source is enabled permanently (SD_EVENT_ON). Note that this event
source type will still allow the event loop to go to sleep again,
even if set to SD_EVENT_ON, as long as no other event source is ever
triggered.
sd_event_add_exit() adds a new event source that will be dispatched
when the event loop is terminated with sd_event_exit(3).
The sd_event_source_set_enabled(3) function may be used to enable the
event source permanently (SD_EVENT_ON) or to make it fire just once
(SD_EVENT_ONESHOT).
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.
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 setting the event source to SD_EVENT_OFF with
sd_event_source_set_enabled(3).
If the second parameter of these functions 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.
On success, these functions return 0 or a positive integer. On
failure, they return a negative errno-style error code.
Returned errors may indicate the following problems:
-ENOMEM
Not enough memory to allocate an object.
-EINVAL
An invalid argument has been passed.
-ESTALE
The event loop is already terminated.
-ECHILD
The event loop has been created in a different process.
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_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_exit(3)
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 2017-07-05. If you dis‐
cover 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 234 SD_EVENT_ADD_DEFER(3)
Pages that refer to this page: sd-event(3), sd_event_add_child(3), sd_event_add_io(3), sd_event_add_signal(3), sd_event_add_time(3), sd_event_exit(3), sd_event_new(3), sd_event_run(3), sd_event_set_watchdog(3), sd_event_source_get_event(3), sd_event_source_get_pending(3), sd_event_source_set_description(3), sd_event_source_set_enabled(3), sd_event_source_set_prepare(3), sd_event_source_set_priority(3), sd_event_source_set_userdata(3), sd_event_source_unref(3), sd_event_wait(3), systemd.directives(7), systemd.index(7)