man/sd_bus_request_name.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7 -->
   8
   9 <refentry id="sd_bus_request_name"
  10           xmlns:xi="http://www.w3.org/2001/XInclude">
  11
  12   <refentryinfo>
  13     <title>sd_bus_request_name</title>
  14     <productname>systemd</productname>
  15   </refentryinfo>
  16
  17   <refmeta>
  18     <refentrytitle>sd_bus_request_name</refentrytitle>
  19     <manvolnum>3</manvolnum>
  20   </refmeta>
  21
  22   <refnamediv>
  23     <refname>sd_bus_request_name</refname>
  24     <refname>sd_bus_request_name_async</refname>
  25     <refname>sd_bus_release_name</refname>
  26     <refname>sd_bus_release_name_async</refname>
  27     <refpurpose>Request or release a well-known service name on a bus</refpurpose>
  28   </refnamediv>
  29
  30   <refsynopsisdiv>
  31     <funcsynopsis>
  32       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  33
  34       <funcprototype>
  35         <funcdef>int <function>sd_bus_request_name</function></funcdef>
  36         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  37         <paramdef>const char *<parameter>name</parameter></paramdef>
  38         <paramdef>uint64_t <parameter>flags</parameter></paramdef>
  39       </funcprototype>
  40
  41       <funcprototype>
  42         <funcdef>int <function>sd_bus_request_name_async</function></funcdef>
  43         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  44         <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
  45         <paramdef>const char *<parameter>name</parameter></paramdef>
  46         <paramdef>uint64_t <parameter>flags</parameter></paramdef>
  47         <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
  48         <paramdef>void *<parameter>userdata</parameter></paramdef>
  49       </funcprototype>
  50
  51       <funcprototype>
  52         <funcdef>int <function>sd_bus_release_name</function></funcdef>
  53         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  54         <paramdef>const char *<parameter>name</parameter></paramdef>
  55       </funcprototype>
  56
  57       <funcprototype>
  58         <funcdef>int <function>sd_bus_release_name_async</function></funcdef>
  59         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  60         <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
  61         <paramdef>const char *<parameter>name</parameter></paramdef>
  62         <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
  63         <paramdef>void *<parameter>userdata</parameter></paramdef>
  64       </funcprototype>
  65     </funcsynopsis>
  66   </refsynopsisdiv>
  67
  68   <refsect1>
  69     <title>Description</title>
  70
  71     <para><function>sd_bus_request_name()</function> requests a well-known service name on a bus. It takes a bus
  72     connection, a valid bus name and a flags parameter. The flags parameter is a combination of the following
  73     flags:</para>
  74
  75     <variablelist>
  76       <varlistentry>
  77         <term><varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname></term>
  78
  79         <listitem><para>After acquiring the name successfully, permit other peers to take over the name when they try
  80         to acquire it with the <varname>SD_BUS_NAME_REPLACE_EXISTING</varname> flag set. If
  81         <varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> is not set on the original request, such a request by other
  82         peers will be denied.</para></listitem>
  83       </varlistentry>
  84
  85       <varlistentry>
  86         <term><varname>SD_BUS_NAME_REPLACE_EXISTING</varname></term>
  87
  88         <listitem><para>Take over the name if it is already acquired by another peer, and that other peer has permitted
  89         takeover by setting <varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> while acquiring it.</para></listitem>
  90       </varlistentry>
  91
  92       <varlistentry>
  93         <term><varname>SD_BUS_NAME_QUEUE</varname></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 <varname>SD_BUS_NAME_QUEUE</varname> 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   </refsect1>
 139
 140   <refsect1>
 141     <title>Errors</title>
 142
 143     <para>Returned errors may indicate the following problems:</para>
 144
 145     <variablelist>
 146       <varlistentry>
 147         <term><constant>-EALREADY</constant></term>
 148
 149         <listitem><para>The caller already is the owner of the specified name.</para></listitem>
 150       </varlistentry>
 151
 152       <varlistentry>
 153         <term><constant>-EEXIST</constant></term>
 154
 155         <listitem><para>The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was
 156         not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the
 157         name.</para></listitem>
 158       </varlistentry>
 159
 160       <varlistentry>
 161         <term><constant>-ESRCH</constant></term>
 162
 163         <listitem><para>It was attempted to release a name that is currently not registered on the
 164         bus.</para></listitem>
 165       </varlistentry>
 166
 167       <varlistentry>
 168         <term><constant>-EADDRINUSE</constant></term>
 169
 170         <listitem><para>It was attempted to release a name that is owned by a different peer on the
 171         bus.</para></listitem>
 172       </varlistentry>
 173
 174       <varlistentry>
 175         <term><constant>-EINVAL</constant></term>
 176
 177         <listitem><para>A specified parameter is invalid. This is also generated when the requested name is a special
 178         service name reserved by the D-Bus specification, or when the operation is requested on a connection that does
 179         not refer to a bus.</para></listitem>
 180       </varlistentry>
 181
 182       <varlistentry>
 183         <term><constant>-ENOTCONN</constant></term>
 184
 185         <listitem><para>The bus connection has been disconnected.</para></listitem>
 186       </varlistentry>
 187
 188       <varlistentry>
 189         <term><constant>-ECHILD</constant></term>
 190
 191         <listitem><para>The bus connection has been created in a different process than the current
 192         one.</para></listitem>
 193       </varlistentry>
 194     </variablelist>
 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>