<?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_signal_to</refname> <refname>sd_bus_emit_signal_tov</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_signal_to</function></funcdef> <paramdef>sd_bus *<parameter>bus</parameter></paramdef> <paramdef>const char *<parameter>destination</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_signal_tov</function></funcdef> <paramdef>sd_bus *<parameter>bus</parameter></paramdef> <paramdef>const char *<parameter>destination</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_signal_to()</function> and <function>sd_bus_emit_signal_tov()</function> are identical to <function>sd_bus_emit_signal()</function> and <function>sd_bus_emit_signalv()</function>, except that they can emit the signal to a single destination. Give <parameter>destination</parameter> as <constant>NULL</constant> to broadcast the signal.</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, library or module instance.</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>