sd_event_source_set_enabled, sd_event_source_get_enabled, SD_EVENT_ON, SD_EVENT_OFF, SD_EVENT_ONESHOT — Enable or disable event sources
SD_EVENT_ONESHOT= -1, };
sd_event_source_set_enabled() may be used to enable or disable the event
source object specified as
takes one of
SD_EVENT_ON (to enable),
SD_EVENT_OFF (to disable)
SD_EVENT_ONESHOT. If invoked with
SD_EVENT_ONESHOT the event
source will be enabled but automatically reset to
SD_EVENT_OFF after one dispatch.
SD_EVENT_OFF, the event source
source may be
NULL, in which case the function does nothing. Otherwise,
source must be a valid pointer to an sd_event_source
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
source is currently enabled or not. If both the
source and the output parameter
NULL, this function returns false. Otherwise,
source must be
a valid pointer to an sd_event_source object. If the output parameter
enabled is not
NULL, it is set to the enablement state (one
SD_EVENT_ONESHOT). The function also returns true if the event source is not
Event source objects are enabled when they are first created
with calls such as
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 pages.
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
with a prior call to
SD_EVENT_OFF, to ensure the event source is
not dispatched again until all other remaining references are dropped.
sd_event_source_set_enabled() returns a non-negative
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.
Functions described here are available as a shared
library, which can be compiled against and linked to with the
The code described here uses
which is declared to be not multi-thread-safe. This means that the code calling the functions described
here must not call
from a parallel thread. It is recommended to only do calls to
from an early phase of the program when no other threads have been started.
sd_event_source_get_enabled() were added in version 229.