man/sd_event_source_get_pending.xml

   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 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="sd_event_source_get_pending" xmlns:xi="http://www.w3.org/2001/XInclude">
   7
   8   <refentryinfo>
   9     <title>sd_event_source_get_pending</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>sd_event_source_get_pending</refentrytitle>
  15     <manvolnum>3</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>sd_event_source_get_pending</refname>
  20
  21     <refpurpose>Determine pending state of event sources</refpurpose>
  22   </refnamediv>
  23
  24   <refsynopsisdiv>
  25     <funcsynopsis>
  26       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  27
  28       <funcprototype>
  29         <funcdef>int <function>sd_event_source_get_pending</function></funcdef>
  30         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  31       </funcprototype>
  32
  33     </funcsynopsis>
  34   </refsynopsisdiv>
  35
  36   <refsect1>
  37     <title>Description</title>
  38
  39     <para><function>sd_event_source_get_pending()</function> may be
  40     used to determine whether the event source object specified as
  41     <parameter>source</parameter> has seen events but has not been
  42     dispatched yet (and thus is marked "pending").</para>
  43
  44     <para>Event source objects initially are not marked pending, when
  45     they are created with calls such as
  46     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  47     <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  48     with the exception of those created with
  49     <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  50     which are immediately marked pending, and
  51     <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  52     for which the "pending" concept is not defined. For details see
  53     the respective manual pages.</para>
  54
  55     <para>In each event loop iteration one event source of those
  56     marked pending is dispatched, in the order defined by the event
  57     source priority, as set with
  58     <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
  59
  60     <para>For I/O event sources, as created with
  61     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  62     the call
  63     <citerefentry><refentrytitle>sd_event_source_get_io_revents</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  64     may be used to query the type of event pending in more
  65     detail.</para>
  66
  67   </refsect1>
  68
  69   <refsect1>
  70     <title>Return Value</title>
  71
  72     <para>On success,
  73     <function>sd_event_source_get_pending()</function> returns an
  74     integer greater than zero when the event source is marked pending,
  75     and zero when the event source is not marked pending. On failure,
  76     it returns a negative errno-style error code.</para>
  77   </refsect1>
  78
  79   <refsect1>
  80     <title>Errors</title>
  81
  82     <para>Returned errors may indicate the following problems:</para>
  83
  84     <variablelist>
  85       <varlistentry>
  86         <term><constant>-EINVAL</constant></term>
  87
  88         <listitem><para><parameter>source</parameter> is not a valid
  89         pointer to an <structname>sd_event_source</structname>
  90         object.</para></listitem>
  91       </varlistentry>
  92
  93       <varlistentry>
  94         <term><constant>-EDOM</constant></term>
  95
  96         <listitem><para><parameter>source</parameter> refers to an
  97         event source object created with
  98         <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
  99       </varlistentry>
 100
 101       <varlistentry>
 102         <term><constant>-ENOMEM</constant></term>
 103
 104         <listitem><para>Not enough memory.</para></listitem>
 105       </varlistentry>
 106
 107       <varlistentry>
 108         <term><constant>-ESTALE</constant></term>
 109
 110         <listitem><para>The event loop is already terminated.</para></listitem>
 111
 112       </varlistentry>
 113
 114       <varlistentry>
 115         <term><constant>-ECHILD</constant></term>
 116
 117         <listitem><para>The event loop has been created in a different process.</para></listitem>
 118
 119       </varlistentry>
 120
 121     </variablelist>
 122   </refsect1>
 123
 124   <xi:include href="libsystemd-pkgconfig.xml" />
 125
 126   <refsect1>
 127     <title>See Also</title>
 128
 129     <para>
 130       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 131       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 132       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 133       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 134       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 135       <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 136       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 137       <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 138     </para>
 139   </refsect1>
 140
 141 </refentry>