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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
+
+ Copyright © 2016 Julian Orth
+-->
+
+<refentry id="sd_bus_process" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+ <refentryinfo>
+ <title>sd_bus_process</title>
+ <productname>systemd</productname>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>sd_bus_process</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_bus_process</refname>
+
+ <refpurpose>Drive the connection</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_bus_process</function></funcdef>
+ <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
+ <paramdef>sd_bus_message **<parameter>ret</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_bus_process()</function> drives the connection between the client and the message bus. That is,
+ it handles connecting, authentication, and message processing. When invoked pending I/O work is executed, and
+ queued incoming messages are dispatched to registered callbacks. Each time it is invoked a single operation is
+ executed. It returns zero when no operations were pending and positive if a message was processed. When zero is
+ returned the caller should synchronously poll for I/O events before calling into
+ <function>sd_bus_process()</function> again. For that either use the simple, synchronous
+ <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry> call, or hook up
+ the bus connection object to an external or manual event loop using
+ <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+ </para>
+
+ <para><function>sd_bus_process()</function> processes at most one incoming message per call. If the parameter
+ <parameter>ret</parameter> is not <constant>NULL</constant> and the call processed a message,
+ <parameter>*ret</parameter> is set to this message. The caller owns a reference to this message and should call
+ <citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> when the
+ message is no longer needed. If <parameter>ret</parameter> is not <constant>NULL</constant>, progress was made, but no message was
+ processed, <parameter>*ret</parameter> is set to <constant>NULL</constant>.</para>
+
+ <para>If the bus object is connected to an
+ <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry> event loop (with
+ <citerefentry><refentrytitle>sd_bus_attach_event</refentrytitle><manvolnum>3</manvolnum></citerefentry>), it is not
+ necessary to call <function>sd_bus_process()</function> directly as it is invoked automatically when
+ necessary.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>If progress was made, a positive integer is returned. If no progress was made, 0 is returned. If an
+ error occurs, a negative <varname>errno</varname>-style error code is returned.</para>
+
+ <refsect2>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>-EINVAL</constant></term>
+
+ <listitem><para>An invalid bus object was passed.</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>-ENOTCONN</constant></term>
+
+ <listitem><para>The bus connection has been terminated already.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ECONNRESET</constant></term>
+
+ <listitem><para>The bus connection has been terminated just now.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EBUSY</constant></term>
+
+ <listitem><para>This function is already being called, i.e. <function>sd_bus_process()</function>
+ has been called from a callback function that itself was called by
+ <function>sd_bus_process()</function>.</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_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_bus_attach_event</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>