systemd-stable/man/sd_bus_send.xml

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1+ -->

<refentry id="sd_bus_send"
          xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>sd_bus_send</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_send</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_send</refname>
    <refname>sd_bus_send_to</refname>

    <refpurpose>Queue a D-Bus message for transfer</refpurpose>
  </refnamediv>

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

      <funcprototype>
        <funcdef>int <function>sd_bus_send</function></funcdef>
        <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
        <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
        <paramdef>uint64_t *<parameter>cookie</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_send_to</function></funcdef>
        <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
        <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
        <paramdef>const char *<parameter>destination</parameter></paramdef>
        <paramdef>uint64_t *<parameter>cookie</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_bus_send()</function> queues the bus message object <parameter>m</parameter> for
    transfer. If <parameter>bus</parameter> is <constant>NULL</constant>, the bus that
    <parameter>m</parameter> is attached to is used. <parameter>bus</parameter> only needs to be set when the
    message is sent to a different bus than the one it's attached to, for example when forwarding messages.
    If the output parameter <parameter>cookie</parameter> is not <constant>NULL</constant>, it is set to the
    message identifier. This value can later be used to match incoming replies to their corresponding
    messages. If <parameter>cookie</parameter> is set to <constant>NULL</constant> and the message is not
    sealed, <function>sd_bus_send()</function> assumes the message <parameter>m</parameter> doesn't expect a
    reply and adds the necessary headers to indicate this.</para>

    <para>Note that in most scenarios, <function>sd_bus_send()</function> should not be called
    directly. Instead, use higher level functions such as
    <citerefentry><refentrytitle>sd_bus_call_method</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
    <citerefentry><refentrytitle>sd_bus_reply_method_return</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    which call <function>sd_bus_send()</function> internally.</para>

    <para><function>sd_bus_send_to()</function> is a shorthand for sending a message to a specific
    destination. It's main use case is to simplify sending unicast signal messages (signals that only have a
    single receiver). It's behavior is similar to calling
    <citerefentry><refentrytitle>sd_bus_message_set_destination</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    followed by calling <function>sd_bus_send()</function>.</para>
  </refsect1>

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

    <para>On success, these functions return a non-negative integer. On failure, they return a negative
    errno-style error code.</para>

    <refsect2 id='errors'>
      <title>Errors</title>

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

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

          <listitem><para>The input parameter <parameter>m</parameter> is <constant>NULL</constant>.
          </para></listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-EOPNOTSUPP</constant></term>

          <listitem><para>The bus connection does not support sending file descriptors.
          </para></listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-ECHILD</constant></term>

          <listitem><para>The bus connection was allocated in a parent process and is being reused in a child
          process after <function>fork()</function>.</para></listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-ENOBUFS</constant></term>

          <listitem><para>The bus connection's write queue is full.</para></listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-ENOTCONN</constant></term>

          <listitem><para>The input parameter <parameter>bus</parameter> is
          <constant>NULL</constant> or the bus is not connected.</para></listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-ECONNRESET</constant></term>

          <listitem><para>The bus connection was closed while waiting for the response.
          </para></listitem>
        </varlistentry>

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

          <listitem><para>Memory allocation failed.</para></listitem>
        </varlistentry>
      </variablelist>
    </refsect2>
  </refsect1>

  <xi:include href="libsystemd-pkgconfig.xml" />

  <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_call_method</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_message_set_destination</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_reply_method_return</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>