man/sd_bus_request_name.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_request_name"
   7           xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>sd_bus_request_name</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>sd_bus_request_name</refentrytitle>
  16     <manvolnum>3</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>sd_bus_request_name</refname>
  21     <refname>sd_bus_request_name_async</refname>
  22     <refname>sd_bus_release_name</refname>
  23     <refname>sd_bus_release_name_async</refname>
  24     <refpurpose>Request or release a well-known service name on a bus</refpurpose>
  25   </refnamediv>
  26
  27   <refsynopsisdiv>
  28     <funcsynopsis>
  29       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  30
  31       <xi:include href="sd_bus_add_match.xml" xpointer="sd_bus_message_handler_t"/>
  32
  33       <funcprototype>
  34         <funcdef>int <function>sd_bus_request_name</function></funcdef>
  35         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  36         <paramdef>const char *<parameter>name</parameter></paramdef>
  37         <paramdef>uint64_t <parameter>flags</parameter></paramdef>
  38       </funcprototype>
  39
  40       <funcprototype>
  41         <funcdef>int <function>sd_bus_request_name_async</function></funcdef>
  42         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  43         <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
  44         <paramdef>const char *<parameter>name</parameter></paramdef>
  45         <paramdef>uint64_t <parameter>flags</parameter></paramdef>
  46         <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
  47         <paramdef>void *<parameter>userdata</parameter></paramdef>
  48       </funcprototype>
  49
  50       <funcprototype>
  51         <funcdef>int <function>sd_bus_release_name</function></funcdef>
  52         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  53         <paramdef>const char *<parameter>name</parameter></paramdef>
  54       </funcprototype>
  55
  56       <funcprototype>
  57         <funcdef>int <function>sd_bus_release_name_async</function></funcdef>
  58         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  59         <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
  60         <paramdef>const char *<parameter>name</parameter></paramdef>
  61         <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
  62         <paramdef>void *<parameter>userdata</parameter></paramdef>
  63       </funcprototype>
  64     </funcsynopsis>
  65   </refsynopsisdiv>
  66
  67   <refsect1>
  68     <title>Description</title>
  69
  70     <para><function>sd_bus_request_name()</function> requests a well-known service name on a bus. It takes a
  71     bus connection, a valid bus name, and a flags parameter. The flags parameter is a combination of zero or
  72     more of the following flags:</para>
  73
  74     <variablelist>
  75       <varlistentry>
  76         <term><constant>SD_BUS_NAME_ALLOW_REPLACEMENT</constant></term>
  77
  78         <listitem><para>After acquiring the name successfully, permit other peers to take over the name when they try
  79         to acquire it with the <constant>SD_BUS_NAME_REPLACE_EXISTING</constant> flag set. If
  80         <constant>SD_BUS_NAME_ALLOW_REPLACEMENT</constant> is not set on the original request, such a request by other
  81         peers will be denied.</para></listitem>
  82       </varlistentry>
  83
  84       <varlistentry>
  85         <term><constant>SD_BUS_NAME_REPLACE_EXISTING</constant></term>
  86
  87         <listitem><para>Take over the name if it was already acquired by another peer, and that other peer
  88         has permitted takeover by setting <constant>SD_BUS_NAME_ALLOW_REPLACEMENT</constant> while acquiring
  89         it.</para></listitem>
  90       </varlistentry>
  91
  92       <varlistentry>
  93         <term><constant>SD_BUS_NAME_QUEUE</constant></term>
  94
  95         <listitem><para>Queue the acquisition of the name when the name is already taken.</para></listitem>
  96       </varlistentry>
  97     </variablelist>
  98
  99     <para><function>sd_bus_request_name()</function> operates in a synchronous fashion: a message requesting the name
 100     is sent to the bus broker, and the call waits until the broker responds.</para>
 101
 102     <para><function>sd_bus_request_name_async()</function> is an asynchronous version of
 103     <function>sd_bus_release_name()</function>. Instead of waiting for the request to complete, the request message is
 104     enqueued. The specified <parameter>callback</parameter> will be called when the broker's response is received. If
 105     the parameter is specified as <constant>NULL</constant> a default implementation is used instead which will
 106     terminate the connection when the name cannot be acquired. The function returns a slot object in its
 107     <parameter>slot</parameter> parameter — if it is passed as non-<constant>NULL</constant> — which may be used as a
 108     reference to the name request operation. Use
 109     <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to destroy
 110     this reference. Note that destroying the reference will not unregister the name, but simply ensure the specified
 111     callback is no longer called.</para>
 112
 113     <para><function>sd_bus_release_name()</function> releases an acquired well-known name. It takes a bus connection
 114     and a valid bus name as parameters. This function operates synchronously, sending a release request message to the
 115     bus broker and waiting for it to reply.</para>
 116
 117     <para><function>sd_bus_release_name_async()</function> is an asynchronous version of
 118     <function>sd_bus_release_name()</function>. The specified <parameter>callback</parameter> function is called when
 119     the name has been released successfully. If specified as <constant>NULL</constant> a generic implementation is used
 120     that ignores the result of the operation. As above, the <parameter>slot</parameter> (if
 121     non-<constant>NULL</constant>) is set to an object that may be used to reference the operation.</para>
 122
 123     <para>These functions are supported only on bus connections, i.e. connections to a bus broker and not on direct
 124     connections.</para>
 125   </refsect1>
 126
 127   <refsect1>
 128     <title>Return Value</title>
 129
 130     <para>On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style
 131     error code.</para>
 132
 133     <para>If <constant>SD_BUS_NAME_QUEUE</constant> is specified, <function>sd_bus_request_name()</function> will return
 134     0 when the name is already taken by another peer and the client has been added to the queue for the name. In that
 135     case, the caller can subscribe to <literal>NameOwnerChanged</literal> signals to be notified when the name is
 136     successfully acquired.  <function>sd_bus_request_name()</function> returns &gt; 0 when the name has immediately
 137     been acquired successfully.</para>
 138
 139     <refsect2>
 140       <title>Errors</title>
 141
 142       <para>Returned errors may indicate the following problems:</para>
 143
 144       <variablelist>
 145         <varlistentry>
 146           <term><constant>-EALREADY</constant></term>
 147
 148           <listitem><para>The caller already is the owner of the specified name.</para></listitem>
 149         </varlistentry>
 150
 151         <varlistentry>
 152           <term><constant>-EEXIST</constant></term>
 153
 154           <listitem><para>The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was
 155           not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the
 156           name.</para></listitem>
 157         </varlistentry>
 158
 159         <varlistentry>
 160           <term><constant>-ESRCH</constant></term>
 161
 162           <listitem><para>It was attempted to release a name that is currently not registered on the
 163           bus.</para></listitem>
 164         </varlistentry>
 165
 166         <varlistentry>
 167           <term><constant>-EADDRINUSE</constant></term>
 168
 169           <listitem><para>It was attempted to release a name that is owned by a different peer on the
 170           bus.</para></listitem>
 171         </varlistentry>
 172
 173         <varlistentry>
 174           <term><constant>-EINVAL</constant></term>
 175
 176           <listitem><para>A specified parameter is invalid. This is also generated when the requested name is
 177           a special service name reserved by the D-Bus specification, or when the operation is requested on a
 178           connection that does not refer to a bus.</para></listitem>
 179         </varlistentry>
 180
 181         <varlistentry>
 182           <term><constant>-ENOTCONN</constant></term>
 183
 184           <listitem><para>The bus connection has been disconnected.</para></listitem>
 185         </varlistentry>
 186
 187         <varlistentry>
 188           <term><constant>-ECHILD</constant></term>
 189
 190           <listitem><para>The bus connection has been created in a different process than the current
 191           one.</para></listitem>
 192         </varlistentry>
 193       </variablelist>
 194     </refsect2>
 195   </refsect1>
 196
 197   <xi:include href="libsystemd-pkgconfig.xml" />
 198
 199   <refsect1>
 200     <title>See Also</title>
 201
 202     <para>
 203       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 204       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 205       <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 206       <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 207     </para>
 208   </refsect1>
 209
 210 </refentry>