sd_event_oneshot(3) — Linux manual page



NAME         top

       sd_event_source_set_enabled, sd_event_source_get_enabled,
       SD_EVENT_ON, SD_EVENT_OFF, SD_EVENT_ONESHOT - Enable or disable event

SYNOPSIS         top

       #include <systemd/sd-event.h>

       enum {
               SD_EVENT_OFF = 0,
               SD_EVENT_ON = 1,
               SD_EVENT_ONESHOT = -1,

       int sd_event_source_set_enabled(sd_event_source *source,
                                       int enabled);

       int sd_event_source_get_enabled(sd_event_source *source,
                                       int *enabled);

DESCRIPTION         top

       sd_event_source_set_enabled() may be used to enable or disable the
       event source object specified as source. The enabled parameter takes
       one of SD_EVENT_ON (to enable), SD_EVENT_OFF (to disable) or
       SD_EVENT_ONESHOT. If invoked with SD_EVENT_ONESHOT the event source
       will be enabled but automatically reset to SD_EVENT_OFF after the
       event source was dispatched once.

       Event sources that are disabled will not result in event loop wakeups
       and will not be dispatched, until they are enabled again.

       sd_event_source_get_enabled() may be used to query whether the event
       source object source is currently enabled or not. It returns the
       enablement state (one of SD_EVENT_ON, SD_EVENT_OFF, SD_EVENT_ONESHOT)
       in enabled, if it is not NULL. It also returns true if the event
       source is not disabled.

       Event source objects are enabled when they are first created with
       calls such as sd_event_add_io(3), sd_event_add_time(3). However,
       depending on the event source type they are enabled continuously
       (SD_EVENT_ON) or only for a single invocation of the event source
       handler (SD_EVENT_ONESHOT). For details see the respective manual

       As event source objects stay active and may be dispatched as long as
       there is at least one reference to them, in many cases it is a good
       idea to combine a call to sd_event_source_unref(3) with a prior call
       to sd_event_source_set_enabled() with SD_EVENT_OFF, to ensure the
       event source is not dispatched again until all other remaining
       references are dropped.

RETURN VALUE         top

       On success, sd_event_source_set_enabled() returns a non-negative
       integer.  sd_event_source_get_enabled() returns zero if the source is
       disabled (SD_EVENT_OFF) and a positive integer otherwise. On failure,
       they return a negative errno-style error code.

       Returned errors may indicate the following problems:

           source is not a valid pointer to an sd_event_source object.

           Not enough memory.

           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

       sd-event(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_add_defer(3),

COLOPHON         top

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       ⟨⟩.  This
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systemd 246                                   SD_EVENT_SOURCE_SET_ENABLED(3)