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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | HISTORY | SEE ALSO | COLOPHON |
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SD_EVEN..._ENABLED(3) sd_event_source_set_enabled SD_EVEN..._ENABLED(3)
sd_event_source_set_enabled, sd_event_source_get_enabled,
SD_EVENT_ON, SD_EVENT_OFF, SD_EVENT_ONESHOT - Enable or disable
event sources
#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);
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.
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.
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.
sd_event_source_set_enabled() and sd_event_source_get_enabled()
were added in version 229.
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)
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 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
systemd 257~devel SD_EVEN..._ENABLED(3)
Pages that refer to this page: sd-event(3), sd_event_add_child(3), sd_event_add_defer(3), sd_event_add_inotify(3), sd_event_add_io(3), sd_event_add_memory_pressure(3), sd_event_add_signal(3), sd_event_add_time(3), sd_event_source_set_prepare(3), sd_event_source_set_ratelimit(3), sd_event_source_unref(3), systemd.directives(7), systemd.index(7)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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