1<?xml version='1.0'?>
2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4
5<!--
6  SPDX-License-Identifier: LGPL-2.1-or-later
7
8  Copyright © 2016 Julian Orth
9-->
10
11<refentry id="sd_bus_process" xmlns:xi="http://www.w3.org/2001/XInclude">
12
13  <refentryinfo>
14    <title>sd_bus_process</title>
15    <productname>systemd</productname>
16  </refentryinfo>
17
18  <refmeta>
19    <refentrytitle>sd_bus_process</refentrytitle>
20    <manvolnum>3</manvolnum>
21  </refmeta>
22
23  <refnamediv>
24    <refname>sd_bus_process</refname>
25
26    <refpurpose>Drive the connection</refpurpose>
27  </refnamediv>
28
29  <refsynopsisdiv>
30    <funcsynopsis>
31      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
32
33      <funcprototype>
34        <funcdef>int <function>sd_bus_process</function></funcdef>
35        <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
36        <paramdef>sd_bus_message **<parameter>ret</parameter></paramdef>
37      </funcprototype>
38    </funcsynopsis>
39  </refsynopsisdiv>
40
41  <refsect1>
42    <title>Description</title>
43
44    <para><function>sd_bus_process()</function> drives the connection between the client and the message bus. That is,
45    it handles connecting, authentication, and message processing. When invoked pending I/O work is executed, and
46    queued incoming messages are dispatched to registered callbacks. Each time it is invoked a single operation is
47    executed. It returns zero when no operations were pending and positive if a message was processed. When zero is
48    returned the caller should synchronously poll for I/O events before calling into
49    <function>sd_bus_process()</function> again. For that either use the simple, synchronous
50    <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry> call, or hook up
51    the bus connection object to an external or manual event loop using
52    <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
53    </para>
54
55    <para><function>sd_bus_process()</function> processes at most one incoming message per call.  If the parameter
56    <parameter>ret</parameter> is not <constant>NULL</constant> and the call processed a message,
57    <parameter>*ret</parameter> is set to this message.  The caller owns a reference to this message and should call
58    <citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> when the
59    message is no longer needed. If <parameter>ret</parameter> is not <constant>NULL</constant>, progress was made, but no message was
60    processed, <parameter>*ret</parameter> is set to <constant>NULL</constant>.</para>
61
62    <para>If the bus object is connected to an
63    <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry> event loop (with
64    <citerefentry><refentrytitle>sd_bus_attach_event</refentrytitle><manvolnum>3</manvolnum></citerefentry>), it is not
65    necessary to call <function>sd_bus_process()</function> directly as it is invoked automatically when
66    necessary.</para>
67  </refsect1>
68
69  <refsect1>
70    <title>Return Value</title>
71
72    <para>If progress was made, a positive integer is returned. If no progress was made, 0 is returned. If an
73    error occurs, a negative <varname>errno</varname>-style error code is returned.</para>
74
75    <refsect2>
76      <title>Errors</title>
77
78      <para>Returned errors may indicate the following problems:</para>
79
80      <variablelist>
81        <varlistentry>
82          <term><constant>-EINVAL</constant></term>
83
84          <listitem><para>An invalid bus object was passed.</para></listitem>
85        </varlistentry>
86
87        <varlistentry>
88          <term><constant>-ECHILD</constant></term>
89
90          <listitem><para>The bus connection was allocated in a parent process and is being reused in a child
91          process after <function>fork()</function>.</para></listitem>
92        </varlistentry>
93
94        <varlistentry>
95          <term><constant>-ENOTCONN</constant></term>
96
97          <listitem><para>The bus connection has been terminated already.</para></listitem>
98        </varlistentry>
99
100        <varlistentry>
101          <term><constant>-ECONNRESET</constant></term>
102
103          <listitem><para>The bus connection has been terminated just now.</para></listitem>
104        </varlistentry>
105
106        <varlistentry>
107          <term><constant>-EBUSY</constant></term>
108
109          <listitem><para>This function is already being called, i.e. <function>sd_bus_process()</function>
110          has been called from a callback function that itself was called by
111          <function>sd_bus_process()</function>.</para></listitem>
112        </varlistentry>
113      </variablelist>
114    </refsect2>
115  </refsect1>
116
117  <xi:include href="libsystemd-pkgconfig.xml" />
118
119  <refsect1>
120    <title>See Also</title>
121
122    <para>
123      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
124      <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
125      <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
126      <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
127      <citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
128      <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
129      <citerefentry><refentrytitle>sd_bus_attach_event</refentrytitle><manvolnum>3</manvolnum></citerefentry>
130    </para>
131  </refsect1>
132
133</refentry>
134