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.
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:
-EINVALsource is not a valid pointer to an sd_event_source object.
Not enough memory.
The event loop has been created in a different process.
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
page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ 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 firstname.lastname@example.org
systemd 246 SD_EVENT_SOURCE_SET_ENABLED(3)