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-or-later -->
   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_signal_to</refname>
  23     <refname>sd_bus_emit_signal_tov</refname>
  24     <refname>sd_bus_emit_interfaces_added</refname>
  25     <refname>sd_bus_emit_interfaces_added_strv</refname>
  26     <refname>sd_bus_emit_interfaces_removed</refname>
  27     <refname>sd_bus_emit_interfaces_removed_strv</refname>
  28     <refname>sd_bus_emit_properties_changed</refname>
  29     <refname>sd_bus_emit_properties_changed_strv</refname>
  30     <refname>sd_bus_emit_object_added</refname>
  31     <refname>sd_bus_emit_object_removed</refname>
  32
  33     <refpurpose>Convenience functions for emitting (standard) D-Bus signals</refpurpose>
  34   </refnamediv>
  35
  36   <refsynopsisdiv>
  37     <funcsynopsis>
  38       <funcsynopsisinfo>#include &lt;systemd/sd-bus-vtable.h&gt;</funcsynopsisinfo>
  39
  40       <funcprototype>
  41         <funcdef>int <function>sd_bus_emit_signal</function></funcdef>
  42         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  43         <paramdef>const char *<parameter>path</parameter></paramdef>
  44         <paramdef>const char *<parameter>interface</parameter></paramdef>
  45         <paramdef>const char *<parameter>member</parameter></paramdef>
  46         <paramdef>const char *<parameter>types</parameter></paramdef>
  47         <paramdef>...</paramdef>
  48       </funcprototype>
  49
  50       <funcprototype>
  51         <funcdef>int <function>sd_bus_emit_signalv</function></funcdef>
  52         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  53         <paramdef>const char *<parameter>path</parameter></paramdef>
  54         <paramdef>const char *<parameter>interface</parameter></paramdef>
  55         <paramdef>const char *<parameter>member</parameter></paramdef>
  56         <paramdef>const char *<parameter>types</parameter></paramdef>
  57         <paramdef>va_list <parameter>ap</parameter></paramdef>
  58       </funcprototype>
  59
  60       <funcprototype>
  61         <funcdef>int <function>sd_bus_emit_signal_to</function></funcdef>
  62         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  63         <paramdef>const char *<parameter>destination</parameter></paramdef>
  64         <paramdef>const char *<parameter>path</parameter></paramdef>
  65         <paramdef>const char *<parameter>interface</parameter></paramdef>
  66         <paramdef>const char *<parameter>member</parameter></paramdef>
  67         <paramdef>const char *<parameter>types</parameter></paramdef>
  68         <paramdef>...</paramdef>
  69       </funcprototype>
  70
  71       <funcprototype>
  72         <funcdef>int <function>sd_bus_emit_signal_tov</function></funcdef>
  73         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  74         <paramdef>const char *<parameter>destination</parameter></paramdef>
  75         <paramdef>const char *<parameter>path</parameter></paramdef>
  76         <paramdef>const char *<parameter>interface</parameter></paramdef>
  77         <paramdef>const char *<parameter>member</parameter></paramdef>
  78         <paramdef>const char *<parameter>types</parameter></paramdef>
  79         <paramdef>va_list <parameter>ap</parameter></paramdef>
  80       </funcprototype>
  81
  82       <funcprototype>
  83         <funcdef>int <function>sd_bus_emit_interfaces_added</function></funcdef>
  84         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  85         <paramdef>const char *<parameter>path</parameter></paramdef>
  86         <paramdef>const char *<parameter>interface</parameter></paramdef>
  87         <paramdef>...</paramdef>
  88       </funcprototype>
  89
  90       <funcprototype>
  91         <funcdef>int <function>sd_bus_emit_interfaces_added_strv</function></funcdef>
  92         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  93         <paramdef>const char *<parameter>path</parameter></paramdef>
  94         <paramdef>const char **<parameter>interfaces</parameter></paramdef>
  95       </funcprototype>
  96
  97       <funcprototype>
  98         <funcdef>int <function>sd_bus_emit_interfaces_removed</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>...</paramdef>
 103       </funcprototype>
 104
 105       <funcprototype>
 106         <funcdef>int <function>sd_bus_emit_interfaces_removed_strv</function></funcdef>
 107         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
 108         <paramdef>const char *<parameter>path</parameter></paramdef>
 109         <paramdef>const char **<parameter>interfaces</parameter></paramdef>
 110       </funcprototype>
 111
 112       <funcprototype>
 113         <funcdef>int <function>sd_bus_emit_properties_changed</function></funcdef>
 114         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
 115         <paramdef>const char *<parameter>path</parameter></paramdef>
 116         <paramdef>const char *<parameter>interface</parameter></paramdef>
 117         <paramdef>const char *<parameter>name</parameter></paramdef>
 118         <paramdef>...</paramdef>
 119       </funcprototype>
 120
 121       <funcprototype>
 122         <funcdef>int <function>sd_bus_emit_properties_changed_strv</function></funcdef>
 123         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
 124         <paramdef>const char *<parameter>path</parameter></paramdef>
 125         <paramdef>const char *<parameter>interface</parameter></paramdef>
 126         <paramdef>const char **<parameter>names</parameter></paramdef>
 127       </funcprototype>
 128
 129       <funcprototype>
 130         <funcdef>int <function>sd_bus_emit_object_added</function></funcdef>
 131         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
 132         <paramdef>const char *<parameter>path</parameter></paramdef>
 133       </funcprototype>
 134
 135       <funcprototype>
 136         <funcdef>int <function>sd_bus_emit_object_removed</function></funcdef>
 137         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
 138         <paramdef>const char *<parameter>path</parameter></paramdef>
 139       </funcprototype>
 140     </funcsynopsis>
 141   </refsynopsisdiv>
 142
 143   <refsect1>
 144     <title>Description</title>
 145
 146     <para><function>sd_bus_emit_signal()</function> is a convenience function for initializing a
 147     bus message object and emitting the corresponding D-Bus signal. It combines the
 148     <citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 149     <citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
 150     <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 151     functions into a single function call. <function>sd_bus_emit_signalv()</function> is
 152     equivalent to <function>sd_bus_message_append()</function>, except that it is called with a
 153     <literal>va_list</literal> instead of a variable number of arguments.</para>
 154
 155     <para><function>sd_bus_emit_signal_to()</function> and <function>sd_bus_emit_signal_tov()</function> are
 156     identical to <function>sd_bus_emit_signal()</function> and <function>sd_bus_emit_signalv()</function>, except
 157     that they can emit the signal to a single destination. Give <parameter>destination</parameter> as
 158     <constant>NULL</constant> to broadcast the signal.</para>
 159
 160     <para><function>sd_bus_emit_interfaces_added()</function> and
 161     <function>sd_bus_emit_interfaces_removed()</function> are used to implement the
 162     <function>InterfacesAdded</function> and <function>InterfacesRemoved</function> signals of the
 163     <constant>org.freedesktop.DBus.ObjectManager</constant> interface. They take a path whose
 164     interfaces have been modified as an argument and a variable list of interfaces that have been
 165     added or removed, respectively. The final argument passed to
 166     <function>sd_bus_emit_interfaces_added()</function> and
 167     <function>sd_bus_emit_interfaces_removed()</function> <emphasis>must</emphasis> be
 168     <constant>NULL</constant>. This allows both functions to safely determine the number of passed
 169     interface arguments. <function>sd_bus_emit_interfaces_added_strv()</function> and
 170     <function>sd_bus_emit_interfaces_removed_strv()</function> are identical to their respective
 171     counterparts but both take the list of interfaces as a single argument instead of a variable
 172     number of arguments.</para>
 173
 174     <para><function>sd_bus_emit_properties_changed()</function> is used to implement the
 175     <function>PropertiesChanged</function> signal of the
 176     <constant>org.freedesktop.DBus.Properties</constant> interface. It takes an object path,
 177     interface and a variable list of property names as its arguments.  The final argument passed to
 178     <function>sd_bus_emit_properties_changed()</function> <emphasis>must</emphasis> be
 179     <constant>NULL</constant>. This allows it to safely determine the number of passed property
 180     names. <function>sd_bus_emit_properties_changed_strv()</function> is identical to
 181     <function>sd_bus_emit_properties_changed()</function> but takes the list of property names as a
 182     single argument instead of a variable number of arguments.</para>
 183
 184     <para><function>sd_bus_emit_object_added()</function> and
 185     <function>sd_bus_emit_object_removed()</function> are convenience functions for emitting the
 186     <function>InterfacesAdded</function> or <function>InterfacesRemoved</function> signals for all
 187     interfaces registered on a specific object path, respectively. This includes any parent fallback
 188     vtables if they are not overridden by a more applicable child vtable. It also includes all the
 189     standard D-Bus interfaces implemented by sd-bus itself on any registered object.</para>
 190
 191     <para>Note that <function>sd_bus_emit_interfaces_added()</function>,
 192     <function>sd_bus_emit_interfaces_removed()</function>,
 193     <function>sd_bus_emit_object_added()</function> and
 194     <function>sd_bus_emit_object_removed()</function> require an object manager to have been
 195     registered on the given object path or one of its parent object paths using
 196     <citerefentry><refentrytitle>sd_bus_add_object_manager</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 197     </para>
 198   </refsect1>
 199
 200   <refsect1>
 201     <title>Return Value</title>
 202
 203     <para>On success, these functions return a non-negative integer. On failure, they return a
 204     negative errno-style error code.</para>
 205
 206     <refsect2>
 207       <title>Errors</title>
 208
 209       <para>Returned errors may indicate the following problems:</para>
 210
 211       <variablelist>
 212         <varlistentry>
 213           <term><constant>-EINVAL</constant></term>
 214
 215           <listitem><para>One of the required parameters is <constant>NULL</constant> or invalid. A
 216           reserved D-Bus interface was passed as the <replaceable>interface</replaceable> parameter.
 217           </para>
 218
 219           <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 220         </varlistentry>
 221
 222         <varlistentry>
 223           <term><constant>-ENOPKG</constant></term>
 224
 225           <listitem><para>The bus cannot be resolved.</para>
 226
 227           <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 228         </varlistentry>
 229
 230         <varlistentry>
 231           <term><constant>-ECHILD</constant></term>
 232
 233           <listitem><para>The bus was created in a different process, library or module instance.</para>
 234
 235           <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 236         </varlistentry>
 237
 238         <varlistentry>
 239           <term><constant>-ENOMEM</constant></term>
 240
 241           <listitem><para>Memory allocation failed.</para>
 242
 243           <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 244         </varlistentry>
 245
 246         <varlistentry>
 247           <term><constant>-ESRCH</constant></term>
 248
 249           <listitem><para>One of <function>sd_bus_emit_interfaces_added()</function>,
 250           <function>sd_bus_emit_interfaces_removed()</function>,
 251           <function>sd_bus_emit_object_added()</function> or
 252           <function>sd_bus_emit_object_removed()</function> was called on an object without an
 253           object manager registered on its own object path or one of its parent object paths.
 254           </para>
 255
 256           <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 257         </varlistentry>
 258       </variablelist>
 259
 260       <para>See the man pages of
 261       <citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 262       <citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
 263       <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 264       for more possible errors.</para>
 265     </refsect2>
 266   </refsect1>
 267
 268   <xi:include href="libsystemd-pkgconfig.xml" />
 269
 270   <refsect1>
 271     <title>History</title>
 272     <para><function>sd_bus_emit_signal()</function>,
 273     <function>sd_bus_emit_signalv()</function>,
 274     <function>sd_bus_emit_interfaces_added()</function>,
 275     <function>sd_bus_emit_interfaces_added_strv()</function>,
 276     <function>sd_bus_emit_interfaces_removed()</function>,
 277     <function>sd_bus_emit_interfaces_removed_strv()</function>,
 278     <function>sd_bus_emit_properties_changed()</function>,
 279     <function>sd_bus_emit_properties_changed_strv()</function>,
 280     <function>sd_bus_emit_object_added()</function>, and
 281     <function>sd_bus_emit_object_removed()</function> were added in version 246.</para>
 282     <para><function>sd_bus_emit_signal_to()</function> and
 283     <function>sd_bus_emit_signal_tov()</function> were added in version 253.</para>
 284   </refsect1>
 285
 286   <refsect1>
 287     <title>See Also</title>
 288
 289     <para>
 290       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 291       <citerefentry><refentrytitle>busctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 292       <citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 293       <citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 294       <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 295       <citerefentry><refentrytitle>sd_bus_call_method</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 296     </para>
 297   </refsect1>
 298 </refentry>