sd_event_add_exit(3) — Linux manual page


SD_EVENT_ADD_DEFER(3)        sd_event_add_defer        SD_EVENT_ADD_DEFER(3)

NAME         top

       sd_event_add_defer, sd_event_add_post, sd_event_add_exit,
       sd_event_handler_t - Add static event sources to an event loop

SYNOPSIS         top

       #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);

DESCRIPTION         top

       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

       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

       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

       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

       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

       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.

RETURN VALUE         top

       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:

           Not enough memory to allocate an object.

           An invalid argument has been passed.

           The event loop is already terminated.

           The event loop has been created in a different process.

NOTES         top

       These APIs are implemented as a shared library, which can be compiled
       and linked to with the libsystemd pkg-config(1) file.

SEE ALSO         top

       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_add_inotify(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), sd_event_exit(3)

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
       project.  Information about the project can be found at 
       ⟨⟩.  If you have a bug
       report for this manual page, see
       ⟨⟩.  This
       page was obtained from the project's upstream Git repository
       ⟨⟩ 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

systemd 246                                            SD_EVENT_ADD_DEFER(3)

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