Systemd/man/sd_event_source_get_pending.xml

<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<!--
  SPDX-License-Identifier: LGPL-2.1+

  This file is part of systemd.

  Copyright 2015 Lennart Poettering
-->

<refentry id="sd_event_source_get_pending" xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>sd_event_source_get_pending</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>Developer</contrib>
        <firstname>Lennart</firstname>
        <surname>Poettering</surname>
        <email>lennart@poettering.net</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_event_source_get_pending</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_event_source_get_pending</refname>

    <refpurpose>Determine pending state of event sources</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>

      <funcprototype>
        <funcdef>int <function>sd_event_source_get_pending</function></funcdef>
        <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
      </funcprototype>

    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_event_source_get_pending()</function> may be
    used to determine whether the event source object specified as
    <parameter>source</parameter> has seen events but has not been
    dispatched yet (and thus is marked "pending").</para>

    <para>Event source objects initially are not marked pending, when
    they are created with calls such as
    <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
    <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
    with the exception of those created with
    <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    which are immediately marked pending, and
    <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    for which the "pending" concept is not defined. For details see
    the respective manual pages.</para>

    <para>In each event loop iteration one event source of those
    marked pending is dispatched, in the order defined by the event
    source priority, as set with
    <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>

    <para>For I/O event sources, as created with
    <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
    the call
    <citerefentry><refentrytitle>sd_event_source_get_io_revents</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    may be used to query the type of event pending in more
    detail.</para>

  </refsect1>

  <refsect1>
    <title>Return Value</title>

    <para>On success,
    <function>sd_event_source_get_pending()</function> returns an
    integer greater than zero when the event source is marked pending,
    and zero when the event source is not marked pending. On failure,
    it returns a negative errno-style error code.</para>
  </refsect1>

  <refsect1>
    <title>Errors</title>

    <para>Returned errors may indicate the following problems:</para>

    <variablelist>
      <varlistentry>
        <term><constant>-EINVAL</constant></term>

        <listitem><para><parameter>source</parameter> is not a valid
        pointer to an <structname>sd_event_source</structname>
        object.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-EDOM</constant></term>

        <listitem><para><parameter>source</parameter> refers to an
        event source object created with
        <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-ENOMEM</constant></term>

        <listitem><para>Not enough memory.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-ESTALE</constant></term>

        <listitem><para>The event loop is already terminated.</para></listitem>

      </varlistentry>

      <varlistentry>
        <term><constant>-ECHILD</constant></term>

        <listitem><para>The event loop has been created in a different process.</para></listitem>

      </varlistentry>

    </variablelist>
  </refsect1>

  <xi:include href="libsystemd-pkgconfig.xml" />

  <refsect1>
    <title>See Also</title>

    <para>
      <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>