NAME

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

SYNOPSIS

       #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

       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 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.

NOTES

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

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)