sd_event_source_set_prepare(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | SEE ALSO | COLOPHON

SD_EVENT_SOURCE_SET_PREPARE(3)t_source_set_prepare_SOURCE_SET_PREPARE(3)

NAME         top

       sd_event_source_set_prepare - Set a preparation callback for
       event sources

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 invoked.

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.

   Errors
       Returned errors may indicate the following problems:

       -EINVAL
           source is not a valid pointer to an sd_event_source object.

       -ESTALE
           The event loop is already terminated.

       -ENOMEM
           Not enough memory.

       -ECHILD
           The event loop has been created in a different process.

       -EDOM
           The specified event source has been created with
           sd_event_add_exit(3).

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),
       sd_event_source_set_userdata(3)

COLOPHON         top

       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
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2021-04-01.  (At that
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       (which is not part of the original manual page), send a mail to
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systemd 248                               SD_EVENT_SOURCE_SET_PREPARE(3)

Pages that refer to this page: sd-event(3)sd_event_wait(3)systemd.directives(7)systemd.index(7)