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+<?xml version='1.0'?>
+<!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-or-later -->
+
+<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>
+ <refname>sd_bus_message_send</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>
+
+ <funcprototype>
+ <funcdef>int sd_bus_message_send</funcdef>
+ <paramdef>sd_bus_message *<parameter>m</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>
+
+ <para><function>sd_bus_send()</function>/<function>sd_bus_send_to()</function> will write the message
+ directly to the underlying transport (e.g. kernel socket buffer) if possible. If the connection is not
+ set up fully yet the message is queued locally. If the transport buffers are congested any unwritten
+ message data is queued locally, too. If the connection has been closed or is currently being closed the
+ call fails.
+ <citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry> should
+ be invoked to write out any queued message data to the transport.</para>
+
+ <para><function>sd_bus_message_send()</function> is the same as <function>sd_bus_send()</function> but
+ without the first and last argument. <function>sd_bus_message_send(m)</function> is equivalent to
+ <function>sd_bus_send(sd_bus_message_get_bus(m), m, NULL)</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>,
+ <citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>