man/sd_event_source_get_pending.xml

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  10   Copyright 2015 Lennart Poettering
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  25
  26 <refentry id="sd_event_source_get_pending" xmlns:xi="http://www.w3.org/2001/XInclude">
  27
  28   <refentryinfo>
  29     <title>sd_event_source_get_pending</title>
  30     <productname>systemd</productname>
  31
  32     <authorgroup>
  33       <author>
  34         <contrib>Developer</contrib>
  35         <firstname>Lennart</firstname>
  36         <surname>Poettering</surname>
  37         <email>lennart@poettering.net</email>
  38       </author>
  39     </authorgroup>
  40   </refentryinfo>
  41
  42   <refmeta>
  43     <refentrytitle>sd_event_source_get_pending</refentrytitle>
  44     <manvolnum>3</manvolnum>
  45   </refmeta>
  46
  47   <refnamediv>
  48     <refname>sd_event_source_get_pending</refname>
  49
  50     <refpurpose>Determine pending state of event sources</refpurpose>
  51   </refnamediv>
  52
  53   <refsynopsisdiv>
  54     <funcsynopsis>
  55       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  56
  57       <funcprototype>
  58         <funcdef>int <function>sd_event_source_get_pending</function></funcdef>
  59         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  60       </funcprototype>
  61
  62     </funcsynopsis>
  63   </refsynopsisdiv>
  64
  65   <refsect1>
  66     <title>Description</title>
  67
  68     <para><function>sd_event_source_get_pending()</function> may be
  69     used to determine whether the event source object specified as
  70     <parameter>source</parameter> has seen events but has not been
  71     dispatched yet (and thus is marked "pending").</para>
  72
  73     <para>Event source objects initially are not marked pending, when
  74     they are created with calls such as
  75     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  76     <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  77     with the exception of those created with
  78     <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  79     which are immediately marked pending, and
  80     <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  81     for which the "pending" concept is not defined. For details see
  82     the respective manual pages.</para>
  83
  84     <para>In each event loop iteration one event source of those
  85     marked pending is dispatched, in the order defined by the event
  86     source priority, as set with
  87     <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
  88
  89     <para>For I/O event sources, as created with
  90     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  91     the call
  92     <citerefentry><refentrytitle>sd_event_source_get_io_revents</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  93     may be used to query the type of event pending in more
  94     detail.</para>
  95
  96   </refsect1>
  97
  98   <refsect1>
  99     <title>Return Value</title>
 100
 101     <para>On success,
 102     <function>sd_event_source_get_pending()</function> returns an
 103     integer greater than zero when the event source is marked pending,
 104     and zero when the event source is not marked pending. On failure,
 105     it returns a negative errno-style error code.</para>
 106   </refsect1>
 107
 108   <refsect1>
 109     <title>Errors</title>
 110
 111     <para>Returned errors may indicate the following problems:</para>
 112
 113     <variablelist>
 114       <varlistentry>
 115         <term><constant>-EINVAL</constant></term>
 116
 117         <listitem><para><parameter>source</parameter> is not a valid
 118         pointer to an <structname>sd_event_source</structname>
 119         object.</para></listitem>
 120       </varlistentry>
 121
 122       <varlistentry>
 123         <term><constant>-EDOM</constant></term>
 124
 125         <listitem><para><parameter>source</parameter> refers to an
 126         event source object created with
 127         <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 128       </varlistentry>
 129
 130       <varlistentry>
 131         <term><constant>-ENOMEM</constant></term>
 132
 133         <listitem><para>Not enough memory.</para></listitem>
 134       </varlistentry>
 135
 136       <varlistentry>
 137         <term><constant>-ESTALE</constant></term>
 138
 139         <listitem><para>The event loop is already terminated.</para></listitem>
 140
 141       </varlistentry>
 142
 143       <varlistentry>
 144         <term><constant>-ECHILD</constant></term>
 145
 146         <listitem><para>The event loop has been created in a different process.</para></listitem>
 147
 148       </varlistentry>
 149
 150     </variablelist>
 151   </refsect1>
 152
 153   <xi:include href="libsystemd-pkgconfig.xml" />
 154
 155   <refsect1>
 156     <title>See Also</title>
 157
 158     <para>
 159       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 160       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 161       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 162       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 163       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 164       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 165       <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 166     </para>
 167   </refsect1>
 168
 169 </refentry>