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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.
All functions listed here are thread-agnostic and only a single
thread may operate on a given object at any given time. Different
threads may access the same object at different times. Multiple
independent objects may be used from different threads in
parallel.
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 2026-08-04. (At that
time, the date of the most recent commit that was found in the
repository was 2026-08-03.) 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 262~devel 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 2026-09-09 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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