sd-event: define a new PREPARING state

[thirdparty/systemd.git] / man / sd_bus_new.xml

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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

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<refentry id="sd_bus_new">

  <refentryinfo>
    <title>sd_bus_new</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>A monkey with a typewriter</contrib>
        <firstname>Zbigniew</firstname>
        <surname>Jędrzejewski-Szmek</surname>
        <email>zbyszek@in.waw.pl</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_new</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_new</refname>
    <refname>sd_bus_ref</refname>
    <refname>sd_bus_unref</refname>

    <refpurpose>Create a new bus object and create or destroy references to it</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>

      <funcprototype>
        <funcdef>int <function>sd_bus_new</function></funcdef>
        <paramdef>sd_bus **<parameter>bus</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>sd_bus *<function>sd_bus_ref</function></funcdef>
        <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>sd_bus *<function>sd_bus_unref</function></funcdef>
        <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_bus_new()</function> creates a new bus
    object. This object is reference-counted, and will be destroyed
    when all references are gone. Initially, the caller of this
    function owns the sole reference and the bus object will not be
    connected to any bus. To connect it to a bus, make sure
    to set an address with
    <citerefentry><refentrytitle>sd_bus_set_address</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    or a related call, and then start the connection with
    <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>

    <para>In most cases, it is a better idea to invoke
    <citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
    <citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    or related calls instead of the more low-level
    <function>sd_bus_new()</function> and
    <function>sd_bus_start()</function>. The higher-level calls not
    only allocate a bus object but also start the connection to a
    well-known bus in a single function invocation.</para>

    <para><function>sd_bus_ref()</function> creates a new reference to
    <parameter>bus</parameter>.</para>

    <para><function>sd_bus_unref()</function> destroys a reference to
    <parameter>bus</parameter>. Once the reference count has dropped
    to zero, <parameter>bus</parameter> cannot be used anymore, so
    further calls to <function>sd_bus_ref()</function> or
    <function>sd_bus_unref()</function> are illegal.</para>
  </refsect1>

  <refsect1>
    <title>Return Value</title>

    <para>On success, <function>sd_bus_new()</function> returns 0 or a
    positive integer. On failure, it returns a negative errno-style
    error code.</para>

    <para><function>sd_bus_ref</function> always returns the argument.
    </para>

    <para><function>sd_bus_unref</function> always returns
    <constant>NULL</constant>.</para>
  </refsect1>

  <refsect1>
    <title>Errors</title>

    <para>Returned errors may indicate the following problems:</para>

    <variablelist>
      <varlistentry>
        <term><constant>-ENOMEM</constant></term>

        <listitem><para>Memory allocation failed.</para></listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Notes</title>

    <para><function>sd_bus_new()</function> and other functions
    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_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_open_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_open_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>