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/4.5/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   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, <function>sd_event_source_get_pending()</function> returns an integer greater than zero
  73     when the event source is marked pending, and zero when the event source is not marked pending. On
  74     failure, it returns a negative errno-style error code.</para>
  75
  76     <refsect2>
  77       <title>Errors</title>
  78
  79       <para>Returned errors may indicate the following problems:</para>
  80
  81       <variablelist>
  82         <varlistentry>
  83           <term><constant>-EINVAL</constant></term>
  84
  85           <listitem><para><parameter>source</parameter> is not a valid pointer to an
  86           <structname>sd_event_source</structname> object.</para></listitem>
  87         </varlistentry>
  88
  89         <varlistentry>
  90           <term><constant>-EDOM</constant></term>
  91
  92           <listitem><para><parameter>source</parameter> refers to an event source object created with
  93           <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
  94         </varlistentry>
  95
  96         <varlistentry>
  97           <term><constant>-ENOMEM</constant></term>
  98
  99           <listitem><para>Not enough memory.</para></listitem>
 100         </varlistentry>
 101
 102         <varlistentry>
 103           <term><constant>-ESTALE</constant></term>
 104
 105           <listitem><para>The event loop is already terminated.</para></listitem>
 106
 107         </varlistentry>
 108
 109         <varlistentry>
 110           <term><constant>-ECHILD</constant></term>
 111
 112           <listitem><para>The event loop has been created in a different process, library or module instance.</para></listitem>
 113
 114         </varlistentry>
 115
 116       </variablelist>
 117     </refsect2>
 118   </refsect1>
 119
 120   <xi:include href="libsystemd-pkgconfig.xml" />
 121
 122   <refsect1>
 123     <title>History</title>
 124     <para><function>sd_event_source_get_pending()</function> was added in version 229.</para>
 125   </refsect1>
 126
 127   <refsect1>
 128     <title>See Also</title>
 129
 130     <para><simplelist type="inline">
 131       <member><citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 132       <member><citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 133       <member><citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 134       <member><citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 135       <member><citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 136       <member><citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 137       <member><citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 138       <member><citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 139     </simplelist></para>
 140   </refsect1>
 141
 142 </refentry>