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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+ -->
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>