x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_EVENT_SOURCE_SET_ENABLEsd_event_source_set_enSD_EVENT_SOURCE_SET_ENABLED(3)
NAME
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
#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
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 pages.
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
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 code.
Errors
Returned errors may indicate the following problems:
-EINVAL
source is not a valid pointer to an sd_event_source object.
-ENOMEM
Not enough memory.
-ECHILD
The event loop has been created in a different process, library or
module instance.
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_unref(3),
sd_event_source_set_ratelimit(3)
systemd 254 SD_EVENT_SOURCE_SET_ENABLED(3)
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