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