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-or-later -->
   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>
  82
  83         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
  84       </varlistentry>
  85
  86       <varlistentry>
  87         <term><constant>SD_BUS_NAME_REPLACE_EXISTING</constant></term>
  88
  89         <listitem><para>Take over the name if it was already acquired by another peer, and that other peer
  90         has permitted takeover by setting <constant>SD_BUS_NAME_ALLOW_REPLACEMENT</constant> while acquiring
  91         it.</para>
  92
  93         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
  94       </varlistentry>
  95
  96       <varlistentry>
  97         <term><constant>SD_BUS_NAME_QUEUE</constant></term>
  98
  99         <listitem><para>Queue the acquisition of the name when the name is already taken.</para>
 100
 101         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 102       </varlistentry>
 103     </variablelist>
 104
 105     <para><function>sd_bus_request_name()</function> operates in a synchronous fashion: a message requesting the name
 106     is sent to the bus broker, and the call waits until the broker responds.</para>
 107
 108     <para><function>sd_bus_request_name_async()</function> is an asynchronous version of
 109     <function>sd_bus_request_name()</function>. Instead of waiting for the request to complete, the request message is
 110     enqueued. The specified <parameter>callback</parameter> will be called when the broker's response is received. If
 111     the parameter is specified as <constant>NULL</constant> a default implementation is used instead which will
 112     terminate the connection when the name cannot be acquired. The function returns a slot object in its
 113     <parameter>slot</parameter> parameter — if it is passed as non-<constant>NULL</constant> — which may be used as a
 114     reference to the name request operation. Use
 115     <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to destroy
 116     this reference. Note that destroying the reference will not unregister the name, but simply ensure the specified
 117     callback is no longer called.</para>
 118
 119     <para><function>sd_bus_release_name()</function> releases an acquired well-known name. It takes a bus connection
 120     and a valid bus name as parameters. This function operates synchronously, sending a release request message to the
 121     bus broker and waiting for it to reply.</para>
 122
 123     <para><function>sd_bus_release_name_async()</function> is an asynchronous version of
 124     <function>sd_bus_release_name()</function>. The specified <parameter>callback</parameter> function is called when
 125     the name has been released successfully. If specified as <constant>NULL</constant> a generic implementation is used
 126     that ignores the result of the operation. As above, the <parameter>slot</parameter> (if
 127     non-<constant>NULL</constant>) is set to an object that may be used to reference the operation.</para>
 128
 129     <para>These functions are supported only on bus connections, i.e. connections to a bus broker and not on direct
 130     connections.</para>
 131   </refsect1>
 132
 133   <refsect1>
 134     <title>Return Value</title>
 135
 136     <para>On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style
 137     error code.</para>
 138
 139     <para>If <constant>SD_BUS_NAME_QUEUE</constant> is specified, <function>sd_bus_request_name()</function> will return
 140     0 when the name is already taken by another peer and the client has been added to the queue for the name. In that
 141     case, the caller can subscribe to <literal>NameOwnerChanged</literal> signals to be notified when the name is
 142     successfully acquired.  <function>sd_bus_request_name()</function> returns &gt; 0 when the name has immediately
 143     been acquired successfully.</para>
 144
 145     <refsect2>
 146       <title>Errors</title>
 147
 148       <para>Returned errors may indicate the following problems:</para>
 149
 150       <variablelist>
 151         <varlistentry>
 152           <term><constant>-EALREADY</constant></term>
 153
 154           <listitem><para>The caller already is the owner of the specified name.</para></listitem>
 155         </varlistentry>
 156
 157         <varlistentry>
 158           <term><constant>-EEXIST</constant></term>
 159
 160           <listitem><para>The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was
 161           not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the
 162           name.</para></listitem>
 163         </varlistentry>
 164
 165         <varlistentry>
 166           <term><constant>-ESRCH</constant></term>
 167
 168           <listitem><para>It was attempted to release a name that is currently not registered on the
 169           bus.</para></listitem>
 170         </varlistentry>
 171
 172         <varlistentry>
 173           <term><constant>-EADDRINUSE</constant></term>
 174
 175           <listitem><para>It was attempted to release a name that is owned by a different peer on the
 176           bus.</para></listitem>
 177         </varlistentry>
 178
 179         <varlistentry>
 180           <term><constant>-EINVAL</constant></term>
 181
 182           <listitem><para>A specified parameter is invalid. This is also generated when the requested name is
 183           a special service name reserved by the D-Bus specification, or when the operation is requested on a
 184           connection that does not refer to a bus.</para></listitem>
 185         </varlistentry>
 186
 187         <varlistentry>
 188           <term><constant>-ENOTCONN</constant></term>
 189
 190           <listitem><para>The bus connection has been disconnected.</para></listitem>
 191         </varlistentry>
 192
 193         <varlistentry>
 194           <term><constant>-ECHILD</constant></term>
 195
 196           <listitem><para>The bus connection has been created in a different process than the current
 197           one.</para></listitem>
 198         </varlistentry>
 199       </variablelist>
 200     </refsect2>
 201   </refsect1>
 202
 203   <xi:include href="libsystemd-pkgconfig.xml" />
 204
 205   <refsect1>
 206     <title>History</title>
 207     <para><function>sd_bus_request_name()</function> and
 208     <function>sd_bus_release_name()</function> were added in version 209.</para>
 209     <para><function>sd_bus_request_name_async()</function> and
 210     <function>sd_bus_release_name_async()</function> were added in version 237.</para>
 211   </refsect1>
 212
 213   <refsect1>
 214     <title>See Also</title>
 215
 216     <para>
 217       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 218       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 219       <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 220       <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 221     </para>
 222   </refsect1>
 223
 224 </refentry>