| <?xml version='1.0'?> <!--*-nxml-*--> |
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| Copyright 2013 Lennart Poettering |
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| |
| <refentry id="sd_bus_request_name"> |
| |
| <refentryinfo> |
| <title>sd_bus_request_name</title> |
| <productname>systemd</productname> |
| |
| <authorgroup> |
| <author> |
| <contrib>Developer</contrib> |
| <firstname>Lennart</firstname> |
| <surname>Poettering</surname> |
| <email>lennart@poettering.net</email> |
| </author> |
| </authorgroup> |
| </refentryinfo> |
| |
| <refmeta> |
| <refentrytitle>sd_bus_request_name</refentrytitle> |
| <manvolnum>3</manvolnum> |
| </refmeta> |
| |
| <refnamediv> |
| <refname>sd_bus_request_name</refname> |
| <refname>sd_bus_request_name_async</refname> |
| <refname>sd_bus_release_name</refname> |
| <refname>sd_bus_release_name_async</refname> |
| <refpurpose>Request or release a well-known service name on a bus</refpurpose> |
| </refnamediv> |
| |
| <refsynopsisdiv> |
| <funcsynopsis> |
| <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> |
| |
| <funcprototype> |
| <funcdef>int <function>sd_bus_request_name</function></funcdef> |
| <paramdef>sd_bus *<parameter>bus</parameter></paramdef> |
| <paramdef>const char *<parameter>name</parameter></paramdef> |
| <paramdef>uint64_t <parameter>flags</parameter></paramdef> |
| </funcprototype> |
| |
| <funcprototype> |
| <funcdef>int <function>sd_bus_request_name_async</function></funcdef> |
| <paramdef>sd_bus *<parameter>bus</parameter></paramdef> |
| <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> |
| <paramdef>const char *<parameter>name</parameter></paramdef> |
| <paramdef>uint64_t <parameter>flags</parameter></paramdef> |
| <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> |
| <paramdef>void *<parameter>userdata</parameter></paramdef> |
| </funcprototype> |
| |
| <funcprototype> |
| <funcdef>int <function>sd_bus_release_name</function></funcdef> |
| <paramdef>sd_bus *<parameter>bus</parameter></paramdef> |
| <paramdef>const char *<parameter>name</parameter></paramdef> |
| </funcprototype> |
| |
| <funcprototype> |
| <funcdef>int <function>sd_bus_release_name_async</function></funcdef> |
| <paramdef>sd_bus *<parameter>bus</parameter></paramdef> |
| <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> |
| <paramdef>const char *<parameter>name</parameter></paramdef> |
| <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> |
| <paramdef>void *<parameter>userdata</parameter></paramdef> |
| </funcprototype> |
| </funcsynopsis> |
| </refsynopsisdiv> |
| |
| <refsect1> |
| <title>Description</title> |
| |
| <para><function>sd_bus_request_name()</function> requests a well-known service name on a bus. It takes a bus |
| connection, a valid bus name and a flags parameter. The flags parameter is a combination of the following |
| flags:</para> |
| |
| <variablelist> |
| <varlistentry> |
| <term><varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname></term> |
| |
| <listitem><para>After acquiring the name successfully, permit other peers to take over the name when they try |
| to acquire it with the <varname>SD_BUS_NAME_REPLACE_EXISTING</varname> flag set. If |
| <varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> is not set on the original request, such a request by other |
| peers will be denied.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>SD_BUS_NAME_REPLACE_EXISTING</varname></term> |
| |
| <listitem><para>Take over the name if it is already acquired by another peer, and that other peer has permitted |
| takeover by setting <varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> while acquiring it.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>SD_BUS_NAME_QUEUE</varname></term> |
| |
| <listitem><para>Queue the acquisition of the name when the name is already taken.</para></listitem> |
| </varlistentry> |
| </variablelist> |
| |
| <para><function>sd_bus_request_name()</function> operates in a synchronous fashion: a message requesting the name |
| is sent to the bus broker, and the call waits until the broker responds.</para> |
| |
| <para><function>sd_bus_request_name_async()</function> is an asynchronous version of of |
| <function>sd_bus_release_name()</function>. Instead of waiting for the request to complete, the request message is |
| enqueued. The specified <parameter>callback</parameter> will be called when the broker's response is received. If |
| the parameter is specified as <constant>NULL</constant> a default implementation is used instead which will |
| terminate the connection when the name cannot be acquired. The function returns a slot object in its |
| <parameter>slot</parameter> parameter — if it is passed as non-<constant>NULL</constant> — which may be used as a |
| reference to the name request operation. Use |
| <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to destroy |
| this reference. Note that destroying the reference will not unregister the name, but simply ensure the specified |
| callback is no longer called.</para> |
| |
| <para><function>sd_bus_release_name()</function> releases an acquired well-known name. It takes a bus connection |
| and a valid bus name as parameters. This function operates synchronously, sending a release request message to the |
| bus broker and waiting for it to reply.</para> |
| |
| <para><function>sd_bus_release_name_async()</function> is an asynchronous version of |
| <function>sd_bus_release_name()</function>. The specified <parameter>callback</parameter> function is called when |
| the name has been released successfully. If specified as <constant>NULL</constant> a generic implementation is used |
| that ignores the result of the operation. As above, the <parameter>slot</parameter> (if |
| non-<constant>NULL</constant>) is set to an object that may be used to reference the operation.</para> |
| |
| <para>These functions are supported only on bus connections, i.e. connections to a bus broker and not on direct |
| connections.</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>Return Value</title> |
| |
| <para>On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style |
| error code.</para> |
| |
| <para>If <varname>SD_BUS_NAME_QUEUE</varname> is specified, <function>sd_bus_request_name()</function> will return |
| 0 when the name is already taken by another peer and the client has been added to the queue for the name. In that |
| case, the caller can subscribe to <literal>NameOwnerChanged</literal> signals to be notified when the name is |
| successfully acquired. <function>sd_bus_request_name()</function> returns > 0 when the name has immediately |
| been acquired successfully.</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>Errors</title> |
| |
| <para>Returned errors may indicate the following problems:</para> |
| |
| <variablelist> |
| <varlistentry> |
| <term><constant>-EALREADY</constant></term> |
| |
| <listitem><para>The caller already is the owner of the specified name.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><constant>-EEXIST</constant></term> |
| |
| <listitem><para>The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was |
| not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the |
| name.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><constant>-ESRCH</constant></term> |
| |
| <listitem><para>It was attempted to release a name that is currently not registered on the |
| bus.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><constant>-EADDRINUSE</constant></term> |
| |
| <listitem><para>It was attempted to release a name that is owned by a different peer on the |
| bus.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><constant>-EINVAL</constant></term> |
| |
| <listitem><para>A specified parameter is invalid. This is also generated when the requested name is a special |
| service name reserved by the D-Bus specification, or when the operation is requested on a connection that does |
| not refer to a bus.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><constant>-ENOTCONN</constant></term> |
| |
| <listitem><para>The bus connection has been disconnected.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><constant>-ECHILD</constant></term> |
| |
| <listitem><para>The bus connection has been created in a different process than the current |
| one.</para></listitem> |
| </varlistentry> |
| </variablelist> |
| </refsect1> |
| |
| <refsect1> |
| <title>Notes</title> |
| |
| <para>The <function>sd_bus_acquire_name()</function> and the other interfaces described here are available as a |
| shared library, which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry |
| project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>See Also</title> |
| |
| <para> |
| <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| </para> |
| </refsect1> |
| |
| </refentry> |