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

SD_EVENT_SOURCE_SET_PREPARE(3)ent_source_set_prepareNT_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         top

       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_child(3), sd_event_add_signal(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
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       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org

systemd 233                                   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)