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