sd_event_source_set_enabled

systemd
Developer Lennart Poettering lennart@poettering.net
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 *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 in enabled.

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()` and `sd_event_source_get_enabled()` return a non-negative integer. 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.

## See Also

sd-event 3, sd_event_add_io 3, sd_event_add_time 3, sd_event_add_child 3, sd_event_add_signal 3, sd_event_add_defer 3, sd_event_source_unref 3