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b1de39dec8
Logically, this is better, because we're describing a subset of possible return values. Visually this also looks quite good because groff renders refsect2 much less prominently. Also rewrap things, add <constant> in various places, fix some typos.
134 lines
5.5 KiB
XML
134 lines
5.5 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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SPDX-License-Identifier: LGPL-2.1+
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Copyright © 2016 Julian Orth
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-->
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<refentry id="sd_bus_process" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_bus_process</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_bus_process</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_bus_process</refname>
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<refpurpose>Drive the connection</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_bus_process</function></funcdef>
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<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
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<paramdef>sd_bus_message **<parameter>ret</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_bus_process()</function> drives the connection between the client and the message bus. That is,
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it handles connecting, authentication, and message processing. When invoked pending I/O work is executed, and
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queued incoming messages are dispatched to registered callbacks. Each time it is invoked a single operation is
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executed. It returns zero when no operations were pending and positive if a message was processed. When zero is
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returned the caller should synchronously poll for I/O events before calling into
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<function>sd_bus_process()</function> again. For that either user the simple, synchronous
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<citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry> call, or hook up
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the bus connection object to an external or manual event loop using
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<citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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</para>
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<para><function>sd_bus_process()</function> processes at most one incoming message per call. If the parameter
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<parameter>ret</parameter> is not <constant>NULL</constant> and the call processed a message,
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<parameter>*ret</parameter> is set to this message. The caller owns a reference to this message and should call
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<citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> when the
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message is no longer needed. If <parameter>ret</parameter> is not NULL, progress was made, but no message was
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processed, <parameter>*ret</parameter> is set to <constant>NULL</constant>.</para>
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<para>If a the bus object is connected to an
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<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry> event loop (with
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<citerefentry><refentrytitle>sd_bus_attach_event</refentrytitle><manvolnum>3</manvolnum></citerefentry>), it is not
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necessary to call <function>sd_bus_process()</function> directly as it is invoked automatically when
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necessary.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>If progress was made, a positive integer is returned. If no progress was made, 0 is returned. If an
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error occurs, a negative <varname>errno</varname>-style error code is returned.</para>
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<refsect2>
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<title>Errors</title>
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<para>Returned errors may indicate the following problems:</para>
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<variablelist>
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<varlistentry>
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<term><constant>-EINVAL</constant></term>
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<listitem><para>An invalid bus object was passed.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ECHILD</constant></term>
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<listitem><para>The bus connection was allocated in a parent process and is being reused in a child
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process after <function>fork()</function>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ENOTCONN</constant></term>
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<listitem><para>The bus connection has been terminated already.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ECONNRESET</constant></term>
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<listitem><para>The bus connection has been terminated just now.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EBUSY</constant></term>
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<listitem><para>This function is already being called, i.e. <function>sd_bus_process()</function>
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has been called from a callback function that itself was called by
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<function>sd_bus_process()</function>.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect2>
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</refsect1>
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<xi:include href="libsystemd-pkgconfig.xml" />
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_attach_event</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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