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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
SPDX-License-Identifier: LGPL-2.1+
-->
<refentry id="sd_bus_request_name"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_bus_request_name</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>sd_bus_request_name</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_bus_request_name</refname>
<refname>sd_bus_request_name_async</refname>
<refname>sd_bus_release_name</refname>
<refname>sd_bus_release_name_async</refname>
<refpurpose>Request or release a well-known service name on a bus</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_bus_request_name</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>const char *<parameter>name</parameter></paramdef>
<paramdef>uint64_t <parameter>flags</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_request_name_async</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
<paramdef>const char *<parameter>name</parameter></paramdef>
<paramdef>uint64_t <parameter>flags</parameter></paramdef>
<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
<paramdef>void *<parameter>userdata</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_release_name</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>const char *<parameter>name</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_release_name_async</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
<paramdef>const char *<parameter>name</parameter></paramdef>
<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
<paramdef>void *<parameter>userdata</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_bus_request_name()</function> requests a well-known service name on a bus. It takes a bus
connection, a valid bus name and a flags parameter. The flags parameter is a combination of the following
flags:</para>
<variablelist>
<varlistentry>
<term><constant>SD_BUS_NAME_ALLOW_REPLACEMENT</constant></term>
<listitem><para>After acquiring the name successfully, permit other peers to take over the name when they try
to acquire it with the <constant>SD_BUS_NAME_REPLACE_EXISTING</constant> flag set. If
<constant>SD_BUS_NAME_ALLOW_REPLACEMENT</constant> is not set on the original request, such a request by other
peers will be denied.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>SD_BUS_NAME_REPLACE_EXISTING</constant></term>
<listitem><para>Take over the name if it is already acquired by another peer, and that other peer has permitted
takeover by setting <constant>SD_BUS_NAME_ALLOW_REPLACEMENT</constant> while acquiring it.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>SD_BUS_NAME_QUEUE</constant></term>
<listitem><para>Queue the acquisition of the name when the name is already taken.</para></listitem>
</varlistentry>
</variablelist>
<para><function>sd_bus_request_name()</function> operates in a synchronous fashion: a message requesting the name
is sent to the bus broker, and the call waits until the broker responds.</para>
<para><function>sd_bus_request_name_async()</function> is an asynchronous version of
<function>sd_bus_release_name()</function>. Instead of waiting for the request to complete, the request message is
enqueued. The specified <parameter>callback</parameter> will be called when the broker's response is received. If
the parameter is specified as <constant>NULL</constant> a default implementation is used instead which will
terminate the connection when the name cannot be acquired. The function returns a slot object in its
<parameter>slot</parameter> parameter — if it is passed as non-<constant>NULL</constant> — which may be used as a
reference to the name request operation. Use
<citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to destroy
this reference. Note that destroying the reference will not unregister the name, but simply ensure the specified
callback is no longer called.</para>
<para><function>sd_bus_release_name()</function> releases an acquired well-known name. It takes a bus connection
and a valid bus name as parameters. This function operates synchronously, sending a release request message to the
bus broker and waiting for it to reply.</para>
<para><function>sd_bus_release_name_async()</function> is an asynchronous version of
<function>sd_bus_release_name()</function>. The specified <parameter>callback</parameter> function is called when
the name has been released successfully. If specified as <constant>NULL</constant> a generic implementation is used
that ignores the result of the operation. As above, the <parameter>slot</parameter> (if
non-<constant>NULL</constant>) is set to an object that may be used to reference the operation.</para>
<para>These functions are supported only on bus connections, i.e. connections to a bus broker and not on direct
connections.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style
error code.</para>
<para>If <constant>SD_BUS_NAME_QUEUE</constant> is specified, <function>sd_bus_request_name()</function> will return
0 when the name is already taken by another peer and the client has been added to the queue for the name. In that
case, the caller can subscribe to <literal>NameOwnerChanged</literal> signals to be notified when the name is
successfully acquired. <function>sd_bus_request_name()</function> returns > 0 when the name has immediately
been acquired successfully.</para>
</refsect1>
<refsect1>
<title>Errors</title>
<para>Returned errors may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><constant>-EALREADY</constant></term>
<listitem><para>The caller already is the owner of the specified name.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-EEXIST</constant></term>
<listitem><para>The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was
not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the
name.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ESRCH</constant></term>
<listitem><para>It was attempted to release a name that is currently not registered on the
bus.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-EADDRINUSE</constant></term>
<listitem><para>It was attempted to release a name that is owned by a different peer on the
bus.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-EINVAL</constant></term>
<listitem><para>A specified parameter is invalid. This is also generated when the requested name is a special
service name reserved by the D-Bus specification, or when the operation is requested on a connection that does
not refer to a bus.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ENOTCONN</constant></term>
<listitem><para>The bus connection has been disconnected.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ECHILD</constant></term>
<listitem><para>The bus connection has been created in a different process than the current
one.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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