225 lines
9.6 KiB
XML
225 lines
9.6 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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SPDX-License-Identifier: LGPL-2.1+
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-->
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<refentry id="sd_bus_request_name">
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<refentryinfo>
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<title>sd_bus_request_name</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_bus_request_name</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_request_name</refname>
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<refname>sd_bus_request_name_async</refname>
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<refname>sd_bus_release_name</refname>
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<refname>sd_bus_release_name_async</refname>
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<refpurpose>Request or release a well-known service name on a bus</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.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_bus_request_name</function></funcdef>
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<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
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<paramdef>const char *<parameter>name</parameter></paramdef>
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<paramdef>uint64_t <parameter>flags</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_request_name_async</function></funcdef>
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<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
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<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
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<paramdef>const char *<parameter>name</parameter></paramdef>
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<paramdef>uint64_t <parameter>flags</parameter></paramdef>
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<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
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<paramdef>void *<parameter>userdata</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_release_name</function></funcdef>
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<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
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<paramdef>const char *<parameter>name</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_release_name_async</function></funcdef>
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<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
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<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
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<paramdef>const char *<parameter>name</parameter></paramdef>
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<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
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<paramdef>void *<parameter>userdata</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_request_name()</function> requests a well-known service name on a bus. It takes a bus
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connection, a valid bus name and a flags parameter. The flags parameter is a combination of the following
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flags:</para>
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<variablelist>
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<varlistentry>
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<term><varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname></term>
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<listitem><para>After acquiring the name successfully, permit other peers to take over the name when they try
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to acquire it with the <varname>SD_BUS_NAME_REPLACE_EXISTING</varname> flag set. If
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<varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> is not set on the original request, such a request by other
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peers will be denied.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>SD_BUS_NAME_REPLACE_EXISTING</varname></term>
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<listitem><para>Take over the name if it is already acquired by another peer, and that other peer has permitted
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takeover by setting <varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> while acquiring it.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>SD_BUS_NAME_QUEUE</varname></term>
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<listitem><para>Queue the acquisition of the name when the name is already taken.</para></listitem>
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</varlistentry>
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</variablelist>
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<para><function>sd_bus_request_name()</function> operates in a synchronous fashion: a message requesting the name
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is sent to the bus broker, and the call waits until the broker responds.</para>
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<para><function>sd_bus_request_name_async()</function> is an asynchronous version of
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<function>sd_bus_release_name()</function>. Instead of waiting for the request to complete, the request message is
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enqueued. The specified <parameter>callback</parameter> will be called when the broker's response is received. If
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the parameter is specified as <constant>NULL</constant> a default implementation is used instead which will
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terminate the connection when the name cannot be acquired. The function returns a slot object in its
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<parameter>slot</parameter> parameter — if it is passed as non-<constant>NULL</constant> — which may be used as a
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reference to the name request operation. Use
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<citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to destroy
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this reference. Note that destroying the reference will not unregister the name, but simply ensure the specified
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callback is no longer called.</para>
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<para><function>sd_bus_release_name()</function> releases an acquired well-known name. It takes a bus connection
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and a valid bus name as parameters. This function operates synchronously, sending a release request message to the
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bus broker and waiting for it to reply.</para>
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<para><function>sd_bus_release_name_async()</function> is an asynchronous version of
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<function>sd_bus_release_name()</function>. The specified <parameter>callback</parameter> function is called when
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the name has been released successfully. If specified as <constant>NULL</constant> a generic implementation is used
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that ignores the result of the operation. As above, the <parameter>slot</parameter> (if
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non-<constant>NULL</constant>) is set to an object that may be used to reference the operation.</para>
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<para>These functions are supported only on bus connections, i.e. connections to a bus broker and not on direct
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connections.</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 calls return 0 or a positive integer. On failure, these calls return a negative errno-style
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error code.</para>
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<para>If <varname>SD_BUS_NAME_QUEUE</varname> is specified, <function>sd_bus_request_name()</function> will return
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0 when the name is already taken by another peer and the client has been added to the queue for the name. In that
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case, the caller can subscribe to <literal>NameOwnerChanged</literal> signals to be notified when the name is
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successfully acquired. <function>sd_bus_request_name()</function> returns > 0 when the name has immediately
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been acquired successfully.</para>
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</refsect1>
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<refsect1>
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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>-EALREADY</constant></term>
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<listitem><para>The caller already is the owner of the specified name.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EEXIST</constant></term>
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<listitem><para>The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was
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not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the
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name.</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>It was attempted to release a name that is currently not registered on the
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bus.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EADDRINUSE</constant></term>
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<listitem><para>It was attempted to release a name that is owned by a different peer on the
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bus.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EINVAL</constant></term>
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<listitem><para>A specified parameter is invalid. This is also generated when the requested name is a special
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service name reserved by the D-Bus specification, or when the operation is requested on a connection that does
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not refer to a bus.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ENOTCONN</constant></term>
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<listitem><para>The bus connection has been disconnected.</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 connection has been created in a different process than the current
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one.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>The <function>sd_bus_acquire_name()</function> and the other interfaces described here are available as a
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shared library, which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry
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project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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