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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | HISTORY | SEE ALSO | COLOPHON |
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SD_BUS_EMIT_SIGNAL(3) sd_bus_emit_signal SD_BUS_EMIT_SIGNAL(3)
sd_bus_emit_signal, sd_bus_emit_signalv, sd_bus_emit_signal_to,
sd_bus_emit_signal_tov, sd_bus_emit_interfaces_added,
sd_bus_emit_interfaces_added_strv, sd_bus_emit_interfaces_removed,
sd_bus_emit_interfaces_removed_strv,
sd_bus_emit_properties_changed,
sd_bus_emit_properties_changed_strv, sd_bus_emit_object_added,
sd_bus_emit_object_removed - Convenience functions for emitting
(standard) D-Bus signals
#include <systemd/sd-bus-vtable.h>
int sd_bus_emit_signal(sd_bus *bus, const char *path,
const char *interface, const char *member,
const char *types, ...);
int sd_bus_emit_signalv(sd_bus *bus, const char *path,
const char *interface, const char *member,
const char *types, va_list ap);
int sd_bus_emit_signal_to(sd_bus *bus, const char *destination,
const char *path, const char *interface,
const char *member, const char *types,
...);
int sd_bus_emit_signal_tov(sd_bus *bus, const char *destination,
const char *path,
const char *interface,
const char *member, const char *types,
va_list ap);
int sd_bus_emit_interfaces_added(sd_bus *bus, const char *path,
const char *interface, ...);
int sd_bus_emit_interfaces_added_strv(sd_bus *bus,
const char *path,
char **interfaces);
int sd_bus_emit_interfaces_removed(sd_bus *bus, const char *path,
const char *interface, ...);
int sd_bus_emit_interfaces_removed_strv(sd_bus *bus,
const char *path,
char **interfaces);
int sd_bus_emit_properties_changed(sd_bus *bus, const char *path,
const char *interface,
const char *name, ...);
int sd_bus_emit_properties_changed_strv(sd_bus *bus,
const char *path,
const char *interface,
char **names);
int sd_bus_emit_object_added(sd_bus *bus, const char *path);
int sd_bus_emit_object_removed(sd_bus *bus, const char *path);
sd_bus_emit_signal() is a convenience function for initializing a
bus message object and emitting the corresponding D-Bus signal. It
combines the sd_bus_message_new_signal(3),
sd_bus_message_append(3) and sd_bus_send(3) functions into a
single function call. sd_bus_emit_signalv() is equivalent to
sd_bus_message_append(), except that it is called with a "va_list"
instead of a variable number of arguments.
sd_bus_emit_signal_to() and sd_bus_emit_signal_tov() are identical
to sd_bus_emit_signal() and sd_bus_emit_signalv(), except that
they can emit the signal to a single destination. Give destination
as NULL to broadcast the signal.
sd_bus_emit_interfaces_added() and
sd_bus_emit_interfaces_removed() are used to implement the
InterfacesAdded and InterfacesRemoved signals of the
org.freedesktop.DBus.ObjectManager interface. They take a path
whose interfaces have been modified as an argument and a variable
list of interfaces that have been added or removed, respectively.
The final argument passed to sd_bus_emit_interfaces_added() and
sd_bus_emit_interfaces_removed() must be NULL. This allows both
functions to safely determine the number of passed interface
arguments. sd_bus_emit_interfaces_added_strv() and
sd_bus_emit_interfaces_removed_strv() are identical to their
respective counterparts but both take the list of interfaces as a
single argument instead of a variable number of arguments.
sd_bus_emit_properties_changed() is used to implement the
PropertiesChanged signal of the org.freedesktop.DBus.Properties
interface. It takes an object path, interface and a variable list
of property names as its arguments. The final argument passed to
sd_bus_emit_properties_changed() must be NULL. This allows it to
safely determine the number of passed property names.
sd_bus_emit_properties_changed_strv() is identical to
sd_bus_emit_properties_changed() but takes the list of property
names as a single argument instead of a variable number of
arguments.
sd_bus_emit_object_added() and sd_bus_emit_object_removed() are
convenience functions for emitting the InterfacesAdded or
InterfacesRemoved signals for all interfaces registered on a
specific object path, respectively. This includes any parent
fallback vtables if they are not overridden by a more applicable
child vtable. It also includes all the standard D-Bus interfaces
implemented by sd-bus itself on any registered object.
Note that sd_bus_emit_interfaces_added(),
sd_bus_emit_interfaces_removed(), sd_bus_emit_object_added() and
sd_bus_emit_object_removed() require an object manager to have
been registered on the given object path or one of its parent
object paths using sd_bus_add_object_manager(3).
On success, these functions return a non-negative integer. On
failure, they return a negative errno-style error code.
Errors
Returned errors may indicate the following problems:
-EINVAL
One of the required parameters is NULL or invalid. A reserved
D-Bus interface was passed as the interface parameter.
-ENOPKG
The bus cannot be resolved.
-ECHILD
The bus was created in a different process, library or module
instance.
-ENOMEM
Memory allocation failed.
-ESRCH
One of sd_bus_emit_interfaces_added(),
sd_bus_emit_interfaces_removed(), sd_bus_emit_object_added()
or sd_bus_emit_object_removed() was called on an object
without an object manager registered on its own object path or
one of its parent object paths.
See the man pages of sd_bus_message_new_signal(3),
sd_bus_message_append(3) and sd_bus_send(3) for more possible
errors.
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_bus_emit_signal(), sd_bus_emit_interfaces_added(),
sd_bus_emit_interfaces_added_strv(),
sd_bus_emit_interfaces_removed(),
sd_bus_emit_interfaces_removed_strv(),
sd_bus_emit_properties_changed(),
sd_bus_emit_properties_changed_strv(), were added in version 221.
sd_bus_emit_object_added(), and sd_bus_emit_object_removed() were
added in version 222.
sd_bus_emit_signalv() was added in version 246.
sd_bus_emit_signal_to() and sd_bus_emit_signal_tov() were added in
version 253.
sd-bus(3), busctl(1), sd_bus_message_new_signal(3),
sd_bus_message_append(3), sd_bus_send(3), sd_bus_call_method(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 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) 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 258~rc2 SD_BUS_EMIT_SIGNAL(3)
Pages that refer to this page: sd-bus(3), sd_bus_add_object(3), sd_bus_add_object_manager(3), sd_bus_call_method(3), sd_bus_message_new_signal(3), systemd.directives(7), systemd.index(7)
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HTML rendering created 2025-09-06 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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