<?xml version='1.0'?> <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"> <!-- SPDX-License-Identifier: LGPL-2.1-or-later Copyright © 2016 Julian Orth --> <refentry id="sd_bus_wait" xmlns:xi="http://www.w3.org/2001/XInclude"> <refentryinfo> <title>sd_bus_wait</title> <productname>systemd</productname> </refentryinfo> <refmeta> <refentrytitle>sd_bus_wait</refentrytitle> <manvolnum>3</manvolnum> </refmeta> <refnamediv> <refname>sd_bus_wait</refname> <refpurpose>Wait for I/O on a bus connection</refpurpose> </refnamediv> <refsynopsisdiv> <funcsynopsis> <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> <funcprototype> <funcdef>int <function>sd_bus_wait</function></funcdef> <paramdef>sd_bus *<parameter>bus</parameter></paramdef> <paramdef>uint64_t <parameter>timeout_usec</parameter></paramdef> </funcprototype> </funcsynopsis> </refsynopsisdiv> <refsect1> <title>Description</title> <para><function>sd_bus_wait()</function> synchronously waits for I/O on the specified bus connection object. This function is supposed to be called whenever <citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry> returns zero, indicating that no work is pending on the connection. Internally, this call invokes <citerefentry project='man-pages'><refentrytitle>ppoll</refentrytitle><manvolnum>2</manvolnum></citerefentry>, to wait for I/O on the bus connection. If the <parameter>timeout_usec</parameter> parameter is specified, the call will block at most for the specified amount of time in μs. Pass <constant>UINT64_MAX</constant> to permit it to sleep indefinitely.</para> <para>After each invocation of <function>sd_bus_wait()</function> the <function>sd_bus_process()</function> call should be invoked in order to process any now pending I/O work.</para> <para>Note that <function>sd_bus_wait()</function> is suitable only for simple programs as it does not permit waiting for other I/O events. For more complex programs either connect the bus connection object to an external event loop using <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry> or to an <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry> event loop using <citerefentry><refentrytitle>sd_bus_attach_event</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> </refsect1> <refsect1> <title>Return Value</title> <para>If any I/O was seen, a positive value is returned, zero otherwise. 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> </variablelist> </refsect2> </refsect1> <xi:include href="libsystemd-pkgconfig.xml" /> <refsect1> <title>History</title> <para><function>sd_bus_wait()</function> was added in version 240.</para> </refsect1> <refsect1> <title>See Also</title> <para><simplelist type="inline"> <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member> <member><citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> <member><citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> <member><citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> <member><citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> <member><citerefentry><refentrytitle>sd_bus_attach_event</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> </simplelist></para> </refsect1> </refentry>