man/sd_bus_request_name.xml

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  10   Copyright 2013 Lennart Poettering
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  25
  26 <refentry id="sd_bus_request_name">
  27
  28   <refentryinfo>
  29     <title>sd_bus_request_name</title>
  30     <productname>systemd</productname>
  31
  32     <authorgroup>
  33       <author>
  34         <contrib>Developer</contrib>
  35         <firstname>Lennart</firstname>
  36         <surname>Poettering</surname>
  37         <email>lennart@poettering.net</email>
  38       </author>
  39     </authorgroup>
  40   </refentryinfo>
  41
  42   <refmeta>
  43     <refentrytitle>sd_bus_request_name</refentrytitle>
  44     <manvolnum>3</manvolnum>
  45   </refmeta>
  46
  47   <refnamediv>
  48     <refname>sd_bus_request_name</refname>
  49     <refname>sd_bus_request_name_async</refname>
  50     <refname>sd_bus_release_name</refname>
  51     <refname>sd_bus_release_name_async</refname>
  52     <refpurpose>Request or release a well-known service name on a bus</refpurpose>
  53   </refnamediv>
  54
  55   <refsynopsisdiv>
  56     <funcsynopsis>
  57       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  58
  59       <funcprototype>
  60         <funcdef>int <function>sd_bus_request_name</function></funcdef>
  61         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  62         <paramdef>const char *<parameter>name</parameter></paramdef>
  63         <paramdef>uint64_t <parameter>flags</parameter></paramdef>
  64       </funcprototype>
  65
  66       <funcprototype>
  67         <funcdef>int <function>sd_bus_request_name_async</function></funcdef>
  68         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  69         <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
  70         <paramdef>const char *<parameter>name</parameter></paramdef>
  71         <paramdef>uint64_t <parameter>flags</parameter></paramdef>
  72         <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
  73         <paramdef>void *<parameter>userdata</parameter></paramdef>
  74       </funcprototype>
  75
  76       <funcprototype>
  77         <funcdef>int <function>sd_bus_release_name</function></funcdef>
  78         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  79         <paramdef>const char *<parameter>name</parameter></paramdef>
  80       </funcprototype>
  81
  82       <funcprototype>
  83         <funcdef>int <function>sd_bus_release_name_async</function></funcdef>
  84         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  85         <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
  86         <paramdef>const char *<parameter>name</parameter></paramdef>
  87         <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
  88         <paramdef>void *<parameter>userdata</parameter></paramdef>
  89       </funcprototype>
  90     </funcsynopsis>
  91   </refsynopsisdiv>
  92
  93   <refsect1>
  94     <title>Description</title>
  95
  96     <para><function>sd_bus_request_name()</function> requests a well-known service name on a bus. It takes a bus
  97     connection, a valid bus name and a flags parameter. The flags parameter is a combination of the following
  98     flags:</para>
  99
 100     <variablelist>
 101       <varlistentry>
 102         <term><varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname></term>
 103
 104         <listitem><para>After acquiring the name successfully, permit other peers to take over the name when they try
 105         to acquire it with the <varname>SD_BUS_NAME_REPLACE_EXISTING</varname> flag set. If
 106         <varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> is not set on the original request, such a request by other
 107         peers will be denied.</para></listitem>
 108       </varlistentry>
 109
 110       <varlistentry>
 111         <term><varname>SD_BUS_NAME_REPLACE_EXISTING</varname></term>
 112
 113         <listitem><para>Take over the name if it is already acquired by another peer, and that other peer has permitted
 114         takeover by setting <varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> while acquiring it.</para></listitem>
 115       </varlistentry>
 116
 117       <varlistentry>
 118         <term><varname>SD_BUS_NAME_QUEUE</varname></term>
 119
 120         <listitem><para>Queue the acquisition of the name when the name is already taken.</para></listitem>
 121       </varlistentry>
 122     </variablelist>
 123
 124     <para><function>sd_bus_request_name()</function> operates in a synchronous fashion: a message requesting the name
 125     is sent to the bus broker, and the call waits until the broker responds.</para>
 126
 127     <para><function>sd_bus_request_name_async()</function> is an asynchronous version of of
 128     <function>sd_bus_release_name()</function>. Instead of waiting for the request to complete, the request message is
 129     enqueued. The specified <parameter>callback</parameter> will be called when the broker's response is received. If
 130     the parameter is specified as <constant>NULL</constant> a default implementation is used instead which will
 131     terminate the connection when the name cannot be acquired. The function returns a slot object in its
 132     <parameter>slot</parameter> parameter — if it is passed as non-<constant>NULL</constant> — which may be used as a
 133     reference to the name request operation. Use
 134     <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to destroy
 135     this reference. Note that destroying the reference will not unregister the name, but simply ensure the specified
 136     callback is no longer called.</para>
 137
 138     <para><function>sd_bus_release_name()</function> releases an acquired well-known name. It takes a bus connection
 139     and a valid bus name as parameters. This function operates synchronously, sending a release request message to the
 140     bus broker and waiting for it to reply.</para>
 141
 142     <para><function>sd_bus_release_name_async()</function> is an asynchronous version of
 143     <function>sd_bus_release_name()</function>. The specified <parameter>callback</parameter> function is called when
 144     the name has been released successfully. If specified as <constant>NULL</constant> a generic implementation is used
 145     that ignores the result of the operation. As above, the <parameter>slot</parameter> (if
 146     non-<constant>NULL</constant>) is set to an object that may be used to reference the operation.</para>
 147
 148     <para>These functions are supported only on bus connections, i.e. connections to a bus broker and not on direct
 149     connections.</para>
 150   </refsect1>
 151
 152   <refsect1>
 153     <title>Return Value</title>
 154
 155     <para>On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style
 156     error code.</para>
 157
 158     <para>If <varname>SD_BUS_NAME_QUEUE</varname> is specified, <function>sd_bus_request_name()</function> will return
 159     0 when the name is already taken by another peer and the client has been added to the queue for the name. In that
 160     case, the caller can subscribe to <literal>NameOwnerChanged</literal> signals to be notified when the name is
 161     successfully acquired.  <function>sd_bus_request_name()</function> returns &gt; 0 when the name has immediately
 162     been acquired successfully.</para>
 163   </refsect1>
 164
 165   <refsect1>
 166     <title>Errors</title>
 167
 168     <para>Returned errors may indicate the following problems:</para>
 169
 170     <variablelist>
 171       <varlistentry>
 172         <term><constant>-EALREADY</constant></term>
 173
 174         <listitem><para>The caller already is the owner of the specified name.</para></listitem>
 175       </varlistentry>
 176
 177       <varlistentry>
 178         <term><constant>-EEXIST</constant></term>
 179
 180         <listitem><para>The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was
 181         not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the
 182         name.</para></listitem>
 183       </varlistentry>
 184
 185       <varlistentry>
 186         <term><constant>-ESRCH</constant></term>
 187
 188         <listitem><para>It was attempted to release a name that is currently not registered on the
 189         bus.</para></listitem>
 190       </varlistentry>
 191
 192       <varlistentry>
 193         <term><constant>-EADDRINUSE</constant></term>
 194
 195         <listitem><para>It was attempted to release a name that is owned by a different peer on the
 196         bus.</para></listitem>
 197       </varlistentry>
 198
 199       <varlistentry>
 200         <term><constant>-EINVAL</constant></term>
 201
 202         <listitem><para>A specified parameter is invalid. This is also generated when the requested name is a special
 203         service name reserved by the D-Bus specification, or when the operation is requested on a connection that does
 204         not refer to a bus.</para></listitem>
 205       </varlistentry>
 206
 207       <varlistentry>
 208         <term><constant>-ENOTCONN</constant></term>
 209
 210         <listitem><para>The bus connection has been disconnected.</para></listitem>
 211       </varlistentry>
 212
 213       <varlistentry>
 214         <term><constant>-ECHILD</constant></term>
 215
 216         <listitem><para>The bus connection has been created in a different process than the current
 217         one.</para></listitem>
 218       </varlistentry>
 219     </variablelist>
 220   </refsect1>
 221
 222   <refsect1>
 223     <title>Notes</title>
 224
 225     <para>The <function>sd_bus_acquire_name()</function> and the other interfaces described here are available as a
 226     shared library, which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry
 227     project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para>
 228   </refsect1>
 229
 230   <refsect1>
 231     <title>See Also</title>
 232
 233     <para>
 234       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 235       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 236       <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 237       <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 238     </para>
 239   </refsect1>
 240
 241 </refentry>