man/sd_event_now.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   Copyright 2015 Lennart Poettering
   9 -->
  10
  11 <refentry id="sd_event_now" xmlns:xi="http://www.w3.org/2001/XInclude">
  12
  13   <refentryinfo>
  14     <title>sd_event_now</title>
  15     <productname>systemd</productname>
  16
  17     <authorgroup>
  18       <author>
  19         <contrib>Developer</contrib>
  20         <firstname>Lennart</firstname>
  21         <surname>Poettering</surname>
  22         <email>lennart@poettering.net</email>
  23       </author>
  24     </authorgroup>
  25   </refentryinfo>
  26
  27   <refmeta>
  28     <refentrytitle>sd_event_now</refentrytitle>
  29     <manvolnum>3</manvolnum>
  30   </refmeta>
  31
  32   <refnamediv>
  33     <refname>sd_event_now</refname>
  34
  35     <refpurpose>Retrieve current event loop iteration timestamp</refpurpose>
  36   </refnamediv>
  37
  38   <refsynopsisdiv>
  39     <funcsynopsis>
  40       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  41
  42       <funcprototype>
  43         <funcdef>int <function>sd_event_now</function></funcdef>
  44         <paramdef>sd_event *<parameter>event</parameter></paramdef>
  45         <paramdef>clockid_t <parameter>clock</parameter></paramdef>
  46         <paramdef>uint64_t *<parameter>usec</parameter></paramdef>
  47       </funcprototype>
  48
  49     </funcsynopsis>
  50   </refsynopsisdiv>
  51
  52   <refsect1>
  53     <title>Description</title>
  54
  55     <para><function>sd_event_now()</function> returns the time when
  56     the most recent event loop iteration began. A timestamp
  57     is taken right after returning from the event sleep, and before
  58     dispatching any event sources. The <parameter>event</parameter>
  59     parameter specifies the event loop object to retrieve the timestamp
  60     from. The <parameter>clock</parameter> parameter specifies the clock to
  61     retrieve the timestamp for, and is one of
  62     <constant>CLOCK_REALTIME</constant> (or equivalently
  63     <constant>CLOCK_REALTIME_ALARM</constant>),
  64     <constant>CLOCK_MONOTONIC</constant>, or
  65     <constant>CLOCK_BOOTTIME</constant> (or equivalently
  66     <constant>CLOCK_BOOTTIME_ALARM</constant>), see
  67     <citerefentry project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
  68     for more information on the various clocks. The retrieved
  69     timestamp is stored in the <parameter>usec</parameter> parameter,
  70     in µs since the clock's epoch. If this function is invoked before
  71     the first event loop iteration, the current time is returned, as
  72     reported by <function>clock_gettime()</function>. To distinguish
  73     this case from a regular invocation the return value will be
  74     positive, and zero when the returned timestamp refers to an actual
  75     event loop iteration.</para>
  76   </refsect1>
  77
  78   <refsect1>
  79     <title>Return Value</title>
  80
  81     <para>If the first event loop iteration has not run yet
  82     <function>sd_event_now()</function> writes current time to
  83     <parameter>usec</parameter> and returns a positive return value.
  84     Otherwise, it will write the requested timestamp to <parameter>usec</parameter>
  85     and return 0. On failure, the call returns a negative errno-style
  86     error code.</para>
  87   </refsect1>
  88
  89   <refsect1>
  90     <title>Errors</title>
  91
  92     <para>Returned values may indicate the following problems:</para>
  93
  94     <variablelist>
  95       <varlistentry>
  96         <term><constant>-EINVAL</constant></term>
  97
  98         <listitem><para>An invalid parameter was
  99         passed.</para></listitem>
 100
 101       </varlistentry>
 102
 103       <varlistentry>
 104         <term><constant>-EOPNOTSUPP</constant></term>
 105
 106         <listitem><para>Unsupported clock type.
 107         </para></listitem>
 108       </varlistentry>
 109
 110       <varlistentry>
 111         <term><constant>-ECHILD</constant></term>
 112
 113         <listitem><para>The event loop object was created in a
 114         different process.</para></listitem>
 115       </varlistentry>
 116     </variablelist>
 117   </refsect1>
 118
 119   <xi:include href="libsystemd-pkgconfig.xml" />
 120
 121   <refsect1>
 122     <title>See Also</title>
 123
 124     <para>
 125       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 126       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 127       <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 128       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 129       <citerefentry project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 130     </para>
 131   </refsect1>
 132
 133 </refentry>