sd_event_source_set_enabled

systemd
sd_event_source_set_enabled
3
sd_event_source_set_enabled
sd_event_source_get_enabled
SD_EVENT_ON
SD_EVENT_OFF
SD_EVENT_ONESHOT
Enable or disable event sources
#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 *
ret
Description
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 one dispatch. For 
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 object.
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. If both the 
source and the output parameter 
ret are 
NULL, this function returns false. Otherwise, 
source must be a valid pointer to an sd_event_source object. If the output parameter 
ret is not 
NULL, it is set to the enablement state (one of 
SD_EVENT_ON, 
SD_EVENT_OFF, 
SD_EVENT_ONESHOT). The function 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 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 
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
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.
Errors
Returned errors may indicate the following problems:
-EINVAL
source is not a valid pointer to an sd_event_source object.
-ENOMEM
Not enough memory.
-ECHILD
The event loop has been created in a different process, library or module instance.
History
sd_event_source_set_enabled() and 
sd_event_source_get_enabled() were added in version 229.
See Also
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), 
sd_event_source_unref(3), 
sd_event_source_set_ratelimit(3)