sd_event_source_set_prepare(3) — Linux manual page



NAME         top

       sd_event_source_set_prepare - Set a preparation callback for event

SYNOPSIS         top

       #include <systemd/sd-event.h>

       int sd_event_source_set_prepare(sd_event_source *source,
                                       sd_event_handler_t callback);

       typedef int (*sd_event_handler_t)(sd_event_source *s,
                                         void *userdata);

DESCRIPTION         top

       sd_event_source_set_prepare() may be used to set a preparation
       callback for the event source object specified as source. The
       callback function specified as callback will be invoked immediately
       before the event loop goes to sleep to wait for incoming events. It
       is invoked with the user data pointer passed when the event source
       was created. The event source will be disabled if the callback
       function returns a negative error code. The callback function may be
       used to reconfigure the precise events to wait for. If the callback
       parameter is passed as NULL the callback function is reset.

       Event source objects have no preparation callback associated when
       they are first created with calls such as sd_event_add_io(3),
       sd_event_add_time(3). Preparation callback functions are supported
       for all event source types with the exception of those created with
       sd_event_add_exit(3). Preparation callback functions are dispatched
       in the order indicated by the event source's priority field, as set
       with sd_event_source_set_priority(3). Preparation callbacks of
       disabled event sources (see sd_event_source_set_enabled(3)) are not

RETURN VALUE         top

       On success, sd_event_source_set_prepare() returns a non-negative
       integer. On failure, it returns a negative errno-style error code.

       Returned errors may indicate the following problems:

           source is not a valid pointer to an sd_event_source object.

           The event loop is already terminated.

           Not enough memory.

           The event loop has been created in a different process.

           The specified event source has been created with

NOTES         top

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

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_set_enabled(3), sd_event_source_set_priority(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 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
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       of the original manual page), send a mail to

systemd 246                                   SD_EVENT_SOURCE_SET_PREPARE(3)

Pages that refer to this page: sd-event(3)sd_event_armed(3)SD_EVENT_ARMED(3)sd_event_dispatch(3)sd_event_exiting(3)SD_EVENT_EXITING(3)sd_event_finished(3)SD_EVENT_FINISHED(3)sd_event_get_iteration(3)sd_event_get_state(3)sd_event_initial(3)SD_EVENT_INITIAL(3)sd_event_pending(3)SD_EVENT_PENDING(3)sd_event_prepare(3)sd_event_preparing(3)SD_EVENT_PREPARING(3)sd_event_running(3)SD_EVENT_RUNNING(3)sd_event_wait(3)30-systemd-environment-d-generator(7)systemd.directives(7)systemd.index(7)