man/sd_event_source_get_pending.xml

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   6   SPDX-License-Identifier: LGPL-2.1+
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   8   Copyright 2015 Lennart Poettering
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  10
  11 <refentry id="sd_event_source_get_pending" xmlns:xi="http://www.w3.org/2001/XInclude">
  12
  13   <refentryinfo>
  14     <title>sd_event_source_get_pending</title>
  15     <productname>systemd</productname>
  16
  17     <authorgroup>
  18       <author>
  19         <contrib>Developer</contrib>
  20         <firstname>Lennart</firstname>
  21         <surname>Poettering</surname>
  22         <email>lennart@poettering.net</email>
  23       </author>
  24     </authorgroup>
  25   </refentryinfo>
  26
  27   <refmeta>
  28     <refentrytitle>sd_event_source_get_pending</refentrytitle>
  29     <manvolnum>3</manvolnum>
  30   </refmeta>
  31
  32   <refnamediv>
  33     <refname>sd_event_source_get_pending</refname>
  34
  35     <refpurpose>Determine pending state of event sources</refpurpose>
  36   </refnamediv>
  37
  38   <refsynopsisdiv>
  39     <funcsynopsis>
  40       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  41
  42       <funcprototype>
  43         <funcdef>int <function>sd_event_source_get_pending</function></funcdef>
  44         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  45       </funcprototype>
  46
  47     </funcsynopsis>
  48   </refsynopsisdiv>
  49
  50   <refsect1>
  51     <title>Description</title>
  52
  53     <para><function>sd_event_source_get_pending()</function> may be
  54     used to determine whether the event source object specified as
  55     <parameter>source</parameter> has seen events but has not been
  56     dispatched yet (and thus is marked "pending").</para>
  57
  58     <para>Event source objects initially are not marked pending, when
  59     they are created with calls such as
  60     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  61     <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  62     with the exception of those created with
  63     <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  64     which are immediately marked pending, and
  65     <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  66     for which the "pending" concept is not defined. For details see
  67     the respective manual pages.</para>
  68
  69     <para>In each event loop iteration one event source of those
  70     marked pending is dispatched, in the order defined by the event
  71     source priority, as set with
  72     <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
  73
  74     <para>For I/O event sources, as created with
  75     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  76     the call
  77     <citerefentry><refentrytitle>sd_event_source_get_io_revents</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  78     may be used to query the type of event pending in more
  79     detail.</para>
  80
  81   </refsect1>
  82
  83   <refsect1>
  84     <title>Return Value</title>
  85
  86     <para>On success,
  87     <function>sd_event_source_get_pending()</function> returns an
  88     integer greater than zero when the event source is marked pending,
  89     and zero when the event source is not marked pending. On failure,
  90     it returns a negative errno-style error code.</para>
  91   </refsect1>
  92
  93   <refsect1>
  94     <title>Errors</title>
  95
  96     <para>Returned errors may indicate the following problems:</para>
  97
  98     <variablelist>
  99       <varlistentry>
 100         <term><constant>-EINVAL</constant></term>
 101
 102         <listitem><para><parameter>source</parameter> is not a valid
 103         pointer to an <structname>sd_event_source</structname>
 104         object.</para></listitem>
 105       </varlistentry>
 106
 107       <varlistentry>
 108         <term><constant>-EDOM</constant></term>
 109
 110         <listitem><para><parameter>source</parameter> refers to an
 111         event source object created with
 112         <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 113       </varlistentry>
 114
 115       <varlistentry>
 116         <term><constant>-ENOMEM</constant></term>
 117
 118         <listitem><para>Not enough memory.</para></listitem>
 119       </varlistentry>
 120
 121       <varlistentry>
 122         <term><constant>-ESTALE</constant></term>
 123
 124         <listitem><para>The event loop is already terminated.</para></listitem>
 125
 126       </varlistentry>
 127
 128       <varlistentry>
 129         <term><constant>-ECHILD</constant></term>
 130
 131         <listitem><para>The event loop has been created in a different process.</para></listitem>
 132
 133       </varlistentry>
 134
 135     </variablelist>
 136   </refsect1>
 137
 138   <xi:include href="libsystemd-pkgconfig.xml" />
 139
 140   <refsect1>
 141     <title>See Also</title>
 142
 143     <para>
 144       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 145       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 146       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 147       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 148       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 149       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 150       <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 151     </para>
 152   </refsect1>
 153
 154 </refentry>