1<?xml version='1.0'?>
2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
5
6<refentry id="sd_event_now" xmlns:xi="http://www.w3.org/2001/XInclude">
7
8  <refentryinfo>
9    <title>sd_event_now</title>
10    <productname>systemd</productname>
11  </refentryinfo>
12
13  <refmeta>
14    <refentrytitle>sd_event_now</refentrytitle>
15    <manvolnum>3</manvolnum>
16  </refmeta>
17
18  <refnamediv>
19    <refname>sd_event_now</refname>
20
21    <refpurpose>Retrieve current event loop iteration timestamp</refpurpose>
22  </refnamediv>
23
24  <refsynopsisdiv>
25    <funcsynopsis>
26      <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
27
28      <funcprototype>
29        <funcdef>int <function>sd_event_now</function></funcdef>
30        <paramdef>sd_event *<parameter>event</parameter></paramdef>
31        <paramdef>clockid_t <parameter>clock</parameter></paramdef>
32        <paramdef>uint64_t *<parameter>usec</parameter></paramdef>
33      </funcprototype>
34
35    </funcsynopsis>
36  </refsynopsisdiv>
37
38  <refsect1>
39    <title>Description</title>
40
41    <para><function>sd_event_now()</function> returns the time when
42    the most recent event loop iteration began. A timestamp
43    is taken right after returning from the event sleep, and before
44    dispatching any event sources. The <parameter>event</parameter>
45    parameter specifies the event loop object to retrieve the timestamp
46    from. The <parameter>clock</parameter> parameter specifies the clock to
47    retrieve the timestamp for, and is one of
48    <constant>CLOCK_REALTIME</constant> (or equivalently
49    <constant>CLOCK_REALTIME_ALARM</constant>),
50    <constant>CLOCK_MONOTONIC</constant>, or
51    <constant>CLOCK_BOOTTIME</constant> (or equivalently
52    <constant>CLOCK_BOOTTIME_ALARM</constant>), see
53    <citerefentry project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
54    for more information on the various clocks. The retrieved
55    timestamp is stored in the <parameter>usec</parameter> parameter,
56    in µs since the clock's epoch. If this function is invoked before
57    the first event loop iteration, the current time is returned, as
58    reported by <function>clock_gettime()</function>. To distinguish
59    this case from a regular invocation the return value will be
60    positive, and zero when the returned timestamp refers to an actual
61    event loop iteration.</para>
62  </refsect1>
63
64  <refsect1>
65    <title>Return Value</title>
66
67    <para>If the first event loop iteration has not run yet <function>sd_event_now()</function> writes
68    current time to <parameter>usec</parameter> and returns a positive return value.  Otherwise, it will
69    write the requested timestamp to <parameter>usec</parameter> and return 0. On failure, the call returns a
70    negative errno-style error code.</para>
71
72    <refsect2>
73      <title>Errors</title>
74
75      <para>Returned values may indicate the following problems:</para>
76
77      <variablelist>
78        <varlistentry>
79          <term><constant>-EINVAL</constant></term>
80
81          <listitem><para>An invalid parameter was passed.</para></listitem>
82
83        </varlistentry>
84
85        <varlistentry>
86          <term><constant>-EOPNOTSUPP</constant></term>
87
88          <listitem><para>Unsupported clock type.</para></listitem>
89        </varlistentry>
90
91        <varlistentry>
92          <term><constant>-ECHILD</constant></term>
93
94          <listitem><para>The event loop object was created in a different process.</para></listitem>
95        </varlistentry>
96      </variablelist>
97    </refsect2>
98  </refsect1>
99
100  <xi:include href="libsystemd-pkgconfig.xml" />
101
102  <refsect1>
103    <title>See Also</title>
104
105    <para>
106      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
107      <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
108      <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
109      <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
110      <citerefentry project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
111    </para>
112  </refsect1>
113
114</refentry>
115