man/sd_event_source_get_pending.xml

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