man/sd_event_source_get_pending.xml

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  23
  24 <refentry id="sd_event_source_get_pending" xmlns:xi="http://www.w3.org/2001/XInclude">
  25
  26   <refentryinfo>
  27     <title>sd_event_source_get_pending</title>
  28     <productname>systemd</productname>
  29
  30     <authorgroup>
  31       <author>
  32         <contrib>Developer</contrib>
  33         <firstname>Lennart</firstname>
  34         <surname>Poettering</surname>
  35         <email>lennart@poettering.net</email>
  36       </author>
  37     </authorgroup>
  38   </refentryinfo>
  39
  40   <refmeta>
  41     <refentrytitle>sd_event_source_get_pending</refentrytitle>
  42     <manvolnum>3</manvolnum>
  43   </refmeta>
  44
  45   <refnamediv>
  46     <refname>sd_event_source_get_pending</refname>
  47
  48     <refpurpose>Determine pending state of event sources</refpurpose>
  49   </refnamediv>
  50
  51   <refsynopsisdiv>
  52     <funcsynopsis>
  53       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  54
  55       <funcprototype>
  56         <funcdef>int <function>sd_event_source_get_pending</function></funcdef>
  57         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  58       </funcprototype>
  59
  60     </funcsynopsis>
  61   </refsynopsisdiv>
  62
  63   <refsect1>
  64     <title>Description</title>
  65
  66     <para><function>sd_event_source_get_pending()</function> may be
  67     used to determine whether the event source object specified as
  68     <parameter>source</parameter> has seen events but has not been
  69     dispatched yet (and thus is marked "pending").</para>
  70
  71     <para>Event source objects initially are not marked pending, when
  72     they are created with calls such as
  73     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  74     <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  75     with the exception of those created with
  76     <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  77     which are immediately marked pending, and
  78     <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  79     for which the "pending" concept is not defined. For details see
  80     the respective manual pages.</para>
  81
  82     <para>In each event loop iteration one event source of those
  83     marked pending is dispatched, in the order defined by the event
  84     source priority, as set with
  85     <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
  86
  87     <para>For I/O event sources, as created with
  88     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  89     the call
  90     <citerefentry><refentrytitle>sd_event_source_get_io_revents</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  91     may be used to query the type of event pending in more
  92     detail.</para>
  93
  94   </refsect1>
  95
  96   <refsect1>
  97     <title>Return Value</title>
  98
  99     <para>On success,
 100     <function>sd_event_source_get_pending()</function> returns an
 101     integer greater than zero when the event source is marked pending,
 102     and zero when the event source is not marked pending. On failure,
 103     it returns a negative errno-style error code.</para>
 104   </refsect1>
 105
 106   <refsect1>
 107     <title>Errors</title>
 108
 109     <para>Returned errors may indicate the following problems:</para>
 110
 111     <variablelist>
 112       <varlistentry>
 113         <term><constant>-EINVAL</constant></term>
 114
 115         <listitem><para><parameter>source</parameter> is not a valid
 116         pointer to an <structname>sd_event_source</structname>
 117         object.</para></listitem>
 118       </varlistentry>
 119
 120       <varlistentry>
 121         <term><constant>-EDOM</constant></term>
 122
 123         <listitem><para><parameter>source</parameter> refers to an
 124         event source object created with
 125         <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 126       </varlistentry>
 127
 128       <varlistentry>
 129         <term><constant>-ENOMEM</constant></term>
 130
 131         <listitem><para>Not enough memory.</para></listitem>
 132       </varlistentry>
 133
 134       <varlistentry>
 135         <term><constant>-ESTALE</constant></term>
 136
 137         <listitem><para>The event loop is already terminated.</para></listitem>
 138
 139       </varlistentry>
 140
 141       <varlistentry>
 142         <term><constant>-ECHILD</constant></term>
 143
 144         <listitem><para>The event loop has been created in a different process.</para></listitem>
 145
 146       </varlistentry>
 147
 148     </variablelist>
 149   </refsect1>
 150
 151   <xi:include href="libsystemd-pkgconfig.xml" />
 152
 153   <refsect1>
 154     <title>See Also</title>
 155
 156     <para>
 157       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 158       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 159       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 160       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 161       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 162       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 163       <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 164     </para>
 165   </refsect1>
 166
 167 </refentry>