x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_EVENT_SOURCE_SET_PREPARsd_event_source_set_prSD_EVENT_SOURCE_SET_PREPARE(3)
NAME
sd_event_source_set_prepare - Set a preparation callback for event
sources
SYNOPSIS
#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
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
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, library or
module instance.
-EDOM
The specified event source has been created with
sd_event_add_exit(3).
NOTES
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 started.
SEE ALSO
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)
systemd 254 SD_EVENT_SOURCE_SET_PREPARE(3)
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