sd_event_source_set_enabled(3) — Linux manual page


SD_EVEN..._ENABLED(3)  sd_event_source_set_enabled SD_EVEN..._ENABLED(3)

NAME         top

       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         top

       #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         top

       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 enabled are 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 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

       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         top

       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

       Returned errors may indicate the following problems:

           source is not a valid pointer to an sd_event_source object.

           Not enough memory.

           The event loop has been created in a different process,
           library or module instance.

NOTES         top

       Functions described here are available as a shared library, which
       can be compiled against and linked to with the
       libsystemd pkg-config(1) file.

       The code described here uses getenv(3), which is declared to be
       not multi-thread-safe. This means that the code calling the
       functions described here must not call setenv(3) from a parallel
       thread. It is recommended to only do calls to setenv() from an
       early phase of the program when no other threads have been

HISTORY         top

       sd_event_source_set_enabled() and sd_event_source_get_enabled()
       were added in version 229.

SEE ALSO         top

       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)

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨⟩.  If you have
       a bug report for this manual page, see
       This page was obtained from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-12-22.)  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

systemd 255                                        SD_EVEN..._ENABLED(3)

Pages that refer to this page: sd-event(3)sd_event_add_child(3)sd_event_add_defer(3)sd_event_add_inotify(3)sd_event_add_io(3)sd_event_add_memory_pressure(3)sd_event_add_signal(3)sd_event_add_time(3)sd_event_source_set_prepare(3)sd_event_source_set_ratelimit(3)sd_event_source_unref(3)systemd.directives(7)systemd.index(7)