systemd/man/sd_bus_request_name.xml

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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_release_name</refname>
    <refpurpose>Request or release a well-known name on a bus</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</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_release_name</function></funcdef>
        <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
        <paramdef>const char *<parameter>name</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_bus_request_name()</function> requests a
    well-known 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_release_name()</function> releases an
    acquired well-known name. It takes a bus connection and a valid
    bus name as parameters.</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 &gt; 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.</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
    <function>sd_bus_release_name()</function> interfaces 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>
    </para>
  </refsect1>

</refentry>