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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="sd_bus_emit_signal"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_bus_emit_signal</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>sd_bus_emit_signal</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_bus_emit_signal</refname>
<refname>sd_bus_emit_signalv</refname>
<refname>sd_bus_emit_interfaces_added</refname>
<refname>sd_bus_emit_interfaces_added_strv</refname>
<refname>sd_bus_emit_interfaces_removed</refname>
<refname>sd_bus_emit_interfaces_removed_strv</refname>
<refname>sd_bus_emit_properties_changed</refname>
<refname>sd_bus_emit_properties_changed_strv</refname>
<refname>sd_bus_emit_object_added</refname>
<refname>sd_bus_emit_object_removed</refname>
<refpurpose>Convenience functions for emitting (standard) D-Bus signals</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-bus-vtable.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_bus_emit_signal</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>const char *<parameter>path</parameter></paramdef>
<paramdef>const char *<parameter>interface</parameter></paramdef>
<paramdef>const char *<parameter>member</parameter></paramdef>
<paramdef>const char *<parameter>types</parameter></paramdef>
<paramdef>...</paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_emit_signalv</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>const char *<parameter>path</parameter></paramdef>
<paramdef>const char *<parameter>interface</parameter></paramdef>
<paramdef>const char *<parameter>member</parameter></paramdef>
<paramdef>const char *<parameter>types</parameter></paramdef>
<paramdef>va_list <parameter>ap</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_emit_interfaces_added</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>const char *<parameter>path</parameter></paramdef>
<paramdef>const char *<parameter>interface</parameter></paramdef>
<paramdef>...</paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_emit_interfaces_added_strv</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>const char *<parameter>path</parameter></paramdef>
<paramdef>const char **<parameter>interfaces</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_emit_interfaces_removed</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>const char *<parameter>path</parameter></paramdef>
<paramdef>const char *<parameter>interface</parameter></paramdef>
<paramdef>...</paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_emit_interfaces_removed_strv</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>const char *<parameter>path</parameter></paramdef>
<paramdef>const char **<parameter>interfaces</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_emit_properties_changed</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>const char *<parameter>path</parameter></paramdef>
<paramdef>const char *<parameter>interface</parameter></paramdef>
<paramdef>const char *<parameter>name</parameter></paramdef>
<paramdef>...</paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_emit_properties_changed_strv</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>const char *<parameter>path</parameter></paramdef>
<paramdef>const char *<parameter>interface</parameter></paramdef>
<paramdef>const char **<parameter>names</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_emit_object_added</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>const char *<parameter>path</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_emit_object_removed</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>const char *<parameter>path</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_bus_emit_signal()</function> is a convenience function for initializing a
bus message object and emitting the corresponding D-Bus signal. It combines the
<citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
<citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>
functions into a single function call. <function>sd_bus_emit_signalv()</function> is
equivalent to <function>sd_bus_message_append()</function>, except that it is called with a
<literal>va_list</literal> instead of a variable number of arguments.</para>
<para><function>sd_bus_emit_interfaces_added()</function> and
<function>sd_bus_emit_interfaces_removed()</function> are used to implement the
<function>InterfacesAdded</function> and <function>InterfacesRemoved</function> signals of the
<constant>org.freedesktop.DBus.ObjectManager</constant> 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
<function>sd_bus_emit_interfaces_added()</function> and
<function>sd_bus_emit_interfaces_removed()</function> <emphasis>must</emphasis> be
<constant>NULL</constant>. This allows both functions to safely determine the number of passed
interface arguments. <function>sd_bus_emit_interfaces_added_strv()</function> and
<function>sd_bus_emit_interfaces_removed_strv()</function> are identical to their respective
counterparts but both take the list of interfaces as a single argument instead of a variable
number of arguments.</para>
<para><function>sd_bus_emit_properties_changed()</function> is used to implement the
<function>PropertiesChanged</function> signal of the
<constant>org.freedesktop.DBus.Properties</constant> interface. It takes an object path,
interface and a variable list of property names as its arguments. The final argument passed to
<function>sd_bus_emit_properties_changed()</function> <emphasis>must</emphasis> be
<constant>NULL</constant>. This allows it to safely determine the number of passed property
names. <function>sd_bus_emit_properties_changed_strv()</function> is identical to
<function>sd_bus_emit_properties_changed()</function> but takes the list of property names as a
single argument instead of a variable number of arguments.</para>
<para><function>sd_bus_emit_object_added()</function> and
<function>sd_bus_emit_object_removed()</function> are convenience functions for emitting the
<function>InterfacesAdded</function> or <function>InterfacesRemoved</function> 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.</para>
<para>Note that <function>sd_bus_emit_interfaces_added()</function>,
<function>sd_bus_emit_interfaces_removed()</function>,
<function>sd_bus_emit_object_added()</function> and
<function>sd_bus_emit_object_removed()</function> require an object manager to have been
registered on the given object path or one of its parent object paths using
<citerefentry><refentrytitle>sd_bus_add_object_manager</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, these functions return a non-negative integer. On failure, they return a
negative errno-style error code.</para>
<refsect2>
<title>Errors</title>
<para>Returned errors may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><constant>-EINVAL</constant></term>
<listitem><para>One of the required parameters is <constant>NULL</constant> or invalid. A
reserved D-Bus interface was passed as the <replaceable>interface</replaceable> parameter.
</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ENOPKG</constant></term>
<listitem><para>The bus cannot be resolved.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ECHILD</constant></term>
<listitem><para>The bus was created in a different process.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ENOMEM</constant></term>
<listitem><para>Memory allocation failed.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ESRCH</constant></term>
<listitem><para>One of <function>sd_bus_emit_interfaces_added()</function>,
<function>sd_bus_emit_interfaces_removed()</function>,
<function>sd_bus_emit_object_added()</function> or
<function>sd_bus_emit_object_removed()</function> was called on an object without an
object manager registered on its own object path or one of its parent object paths.
</para></listitem>
</varlistentry>
</variablelist>
<para>See the man pages of
<citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
<citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>
for more possible errors.</para>
</refsect2>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>busctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_call_method</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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