man/sd_event_source_get_pending.xml

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