man/sd_bus_emit_signal.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="sd_bus_emit_signal"
   7           xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>sd_bus_emit_signal</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>sd_bus_emit_signal</refentrytitle>
  16     <manvolnum>3</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>sd_bus_emit_signal</refname>
  21     <refname>sd_bus_emit_signalv</refname>
  22     <refname>sd_bus_emit_interfaces_added</refname>
  23     <refname>sd_bus_emit_interfaces_added_strv</refname>
  24     <refname>sd_bus_emit_interfaces_removed</refname>
  25     <refname>sd_bus_emit_interfaces_removed_strv</refname>
  26     <refname>sd_bus_emit_properties_changed</refname>
  27     <refname>sd_bus_emit_properties_changed_strv</refname>
  28     <refname>sd_bus_emit_object_added</refname>
  29     <refname>sd_bus_emit_object_removed</refname>
  30
  31     <refpurpose>Convenience functions for emitting (standard) D-Bus signals</refpurpose>
  32   </refnamediv>
  33
  34   <refsynopsisdiv>
  35     <funcsynopsis>
  36       <funcsynopsisinfo>#include &lt;systemd/sd-bus-vtable.h&gt;</funcsynopsisinfo>
  37
  38       <funcprototype>
  39         <funcdef>int <function>sd_bus_emit_signal</function></funcdef>
  40         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  41         <paramdef>const char *<parameter>path</parameter></paramdef>
  42         <paramdef>const char *<parameter>interface</parameter></paramdef>
  43         <paramdef>const char *<parameter>member</parameter></paramdef>
  44         <paramdef>const char *<parameter>types</parameter></paramdef>
  45         <paramdef>...</paramdef>
  46       </funcprototype>
  47
  48       <funcprototype>
  49         <funcdef>int <function>sd_bus_emit_signalv</function></funcdef>
  50         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  51         <paramdef>const char *<parameter>path</parameter></paramdef>
  52         <paramdef>const char *<parameter>interface</parameter></paramdef>
  53         <paramdef>const char *<parameter>member</parameter></paramdef>
  54         <paramdef>const char *<parameter>types</parameter></paramdef>
  55         <paramdef>va_list <parameter>ap</parameter></paramdef>
  56       </funcprototype>
  57
  58       <funcprototype>
  59         <funcdef>int <function>sd_bus_emit_interfaces_added</function></funcdef>
  60         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  61         <paramdef>const char *<parameter>path</parameter></paramdef>
  62         <paramdef>const char *<parameter>interface</parameter></paramdef>
  63         <paramdef>...</paramdef>
  64       </funcprototype>
  65
  66       <funcprototype>
  67         <funcdef>int <function>sd_bus_emit_interfaces_added_strv</function></funcdef>
  68         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  69         <paramdef>const char *<parameter>path</parameter></paramdef>
  70         <paramdef>const char **<parameter>interfaces</parameter></paramdef>
  71       </funcprototype>
  72
  73       <funcprototype>
  74         <funcdef>int <function>sd_bus_emit_interfaces_removed</function></funcdef>
  75         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  76         <paramdef>const char *<parameter>path</parameter></paramdef>
  77         <paramdef>const char *<parameter>interface</parameter></paramdef>
  78         <paramdef>...</paramdef>
  79       </funcprototype>
  80
  81       <funcprototype>
  82         <funcdef>int <function>sd_bus_emit_interfaces_removed_strv</function></funcdef>
  83         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  84         <paramdef>const char *<parameter>path</parameter></paramdef>
  85         <paramdef>const char **<parameter>interfaces</parameter></paramdef>
  86       </funcprototype>
  87
  88       <funcprototype>
  89         <funcdef>int <function>sd_bus_emit_properties_changed</function></funcdef>
  90         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  91         <paramdef>const char *<parameter>path</parameter></paramdef>
  92         <paramdef>const char *<parameter>interface</parameter></paramdef>
  93         <paramdef>const char *<parameter>name</parameter></paramdef>
  94         <paramdef>...</paramdef>
  95       </funcprototype>
  96
  97       <funcprototype>
  98         <funcdef>int <function>sd_bus_emit_properties_changed_strv</function></funcdef>
  99         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
 100         <paramdef>const char *<parameter>path</parameter></paramdef>
 101         <paramdef>const char *<parameter>interface</parameter></paramdef>
 102         <paramdef>const char **<parameter>names</parameter></paramdef>
 103       </funcprototype>
 104
 105       <funcprototype>
 106         <funcdef>int <function>sd_bus_emit_object_added</function></funcdef>
 107         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
 108         <paramdef>const char *<parameter>path</parameter></paramdef>
 109       </funcprototype>
 110
 111       <funcprototype>
 112         <funcdef>int <function>sd_bus_emit_object_removed</function></funcdef>
 113         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
 114         <paramdef>const char *<parameter>path</parameter></paramdef>
 115       </funcprototype>
 116     </funcsynopsis>
 117   </refsynopsisdiv>
 118
 119   <refsect1>
 120     <title>Description</title>
 121
 122     <para><function>sd_bus_emit_signal()</function> is a convenience function for initializing a
 123     bus message object and emitting the corresponding D-Bus signal. It combines the
 124     <citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 125     <citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
 126     <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 127     functions into a single function call. <function>sd_bus_emit_signalv()</function> is
 128     equivalent to <function>sd_bus_message_append()</function>, except that it is called with a
 129     <literal>va_list</literal> instead of a variable number of arguments.</para>
 130
 131     <para><function>sd_bus_emit_interfaces_added()</function> and
 132     <function>sd_bus_emit_interfaces_removed()</function> are used to implement the
 133     <function>InterfacesAdded</function> and <function>InterfacesRemoved</function> signals of the
 134     <constant>org.freedesktop.DBus.ObjectManager</constant> interface. They take a path whose
 135     interfaces have been modified as an argument and a variable list of interfaces that have been
 136     added or removed, respectively. The final argument passed to
 137     <function>sd_bus_emit_interfaces_added()</function> and
 138     <function>sd_bus_emit_interfaces_removed()</function> <emphasis>must</emphasis> be
 139     <constant>NULL</constant>. This allows both functions to safely determine the number of passed
 140     interface arguments. <function>sd_bus_emit_interfaces_added_strv()</function> and
 141     <function>sd_bus_emit_interfaces_removed_strv()</function> are identical to their respective
 142     counterparts but both take the list of interfaces as a single argument instead of a variable
 143     number of arguments.</para>
 144
 145     <para><function>sd_bus_emit_properties_changed()</function> is used to implement the
 146     <function>PropertiesChanged</function> signal of the
 147     <constant>org.freedesktop.DBus.Properties</constant> interface. It takes an object path,
 148     interface and a variable list of property names as its arguments.  The final argument passed to
 149     <function>sd_bus_emit_properties_changed()</function> <emphasis>must</emphasis> be
 150     <constant>NULL</constant>. This allows it to safely determine the number of passed property
 151     names. <function>sd_bus_emit_properties_changed_strv()</function> is identical to
 152     <function>sd_bus_emit_properties_changed()</function> but takes the list of property names as a
 153     single argument instead of a variable number of arguments.</para>
 154
 155     <para><function>sd_bus_emit_object_added()</function> and
 156     <function>sd_bus_emit_object_removed()</function> are convenience functions for emitting the
 157     <function>InterfacesAdded</function> or <function>InterfacesRemoved</function> signals for all
 158     interfaces registered on a specific object path, respectively. This includes any parent fallback
 159     vtables if they are not overridden by a more applicable child vtable. It also includes all the
 160     standard D-Bus interfaces implemented by sd-bus itself on any registered object.</para>
 161
 162     <para>Note that <function>sd_bus_emit_interfaces_added()</function>,
 163     <function>sd_bus_emit_interfaces_removed()</function>,
 164     <function>sd_bus_emit_object_added()</function> and
 165     <function>sd_bus_emit_object_removed()</function> require an object manager to have been
 166     registered on the given object path or one of its parent object paths using
 167     <citerefentry><refentrytitle>sd_bus_add_object_manager</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 168     </para>
 169   </refsect1>
 170
 171   <refsect1>
 172     <title>Return Value</title>
 173
 174     <para>On success, these functions return a non-negative integer. On failure, they return a
 175     negative errno-style error code.</para>
 176
 177     <refsect2>
 178       <title>Errors</title>
 179
 180       <para>Returned errors may indicate the following problems:</para>
 181
 182       <variablelist>
 183         <varlistentry>
 184           <term><constant>-EINVAL</constant></term>
 185
 186           <listitem><para>One of the required parameters is <constant>NULL</constant> or invalid. A
 187           reserved D-Bus interface was passed as the <replaceable>interface</replaceable> parameter.
 188           </para></listitem>
 189         </varlistentry>
 190
 191         <varlistentry>
 192           <term><constant>-ENOPKG</constant></term>
 193
 194           <listitem><para>The bus cannot be resolved.</para></listitem>
 195         </varlistentry>
 196
 197         <varlistentry>
 198           <term><constant>-ECHILD</constant></term>
 199
 200           <listitem><para>The bus was created in a different process.</para></listitem>
 201         </varlistentry>
 202
 203         <varlistentry>
 204           <term><constant>-ENOMEM</constant></term>
 205
 206           <listitem><para>Memory allocation failed.</para></listitem>
 207         </varlistentry>
 208
 209         <varlistentry>
 210           <term><constant>-ESRCH</constant></term>
 211
 212           <listitem><para>One of <function>sd_bus_emit_interfaces_added()</function>,
 213           <function>sd_bus_emit_interfaces_removed()</function>,
 214           <function>sd_bus_emit_object_added()</function> or
 215           <function>sd_bus_emit_object_removed()</function> was called on an object without an
 216           object manager registered on its own object path or one of its parent object paths.
 217           </para></listitem>
 218         </varlistentry>
 219       </variablelist>
 220
 221       <para>See the man pages of
 222       <citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 223       <citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
 224       <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 225       for more possible errors.</para>
 226     </refsect2>
 227   </refsect1>
 228
 229   <xi:include href="libsystemd-pkgconfig.xml" />
 230
 231   <refsect1>
 232     <title>See Also</title>
 233
 234     <para>
 235       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 236       <citerefentry><refentrytitle>busctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 237       <citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 238       <citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 239       <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 240       <citerefentry><refentrytitle>sd_bus_call_method</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 241     </para>
 242   </refsect1>
 243 </refentry>