man/sd_event_now.xml

   1 <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   This file is part of systemd.
   7
   8   Copyright 2015 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
  15   systemd is distributed in the hope that it will be useful, but
  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   Lesser General Public License for more details.
  19
  20   You should have received a copy of the GNU Lesser General Public License
  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22 -->
  23
  24 <refentry id="sd_event_now" xmlns:xi="http://www.w3.org/2001/XInclude">
  25
  26   <refentryinfo>
  27     <title>sd_event_now</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_now</refentrytitle>
  42     <manvolnum>3</manvolnum>
  43   </refmeta>
  44
  45   <refnamediv>
  46     <refname>sd_event_now</refname>
  47
  48     <refpurpose>Retrieve current event loop iteration timestamp</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_now</function></funcdef>
  57         <paramdef>sd_event *<parameter>event</parameter></paramdef>
  58         <paramdef>clockid_t <parameter>clock</parameter></paramdef>
  59         <paramdef>uint64_t *<parameter>usec</parameter></paramdef>
  60       </funcprototype>
  61
  62     </funcsynopsis>
  63   </refsynopsisdiv>
  64
  65   <refsect1>
  66     <title>Description</title>
  67
  68     <para><function>sd_event_now()</function> returns the time when
  69     the most recent event loop iteration began. A timestamp
  70     is taken right after returning from the event sleep, and before
  71     dispatching any event sources. The <parameter>event</parameter>
  72     parameter specifies the event loop object to retrieve the timestamp
  73     from. The <parameter>clock</parameter> parameter specifies the clock to
  74     retrieve the timestamp for, and is one of
  75     <constant>CLOCK_REALTIME</constant> (or equivalently
  76     <constant>CLOCK_REALTIME_ALARM</constant>),
  77     <constant>CLOCK_MONOTONIC</constant>, or
  78     <constant>CLOCK_BOOTTIME</constant> (or equivalently
  79     <constant>CLOCK_BOOTTIME_ALARM</constant>), see
  80     <citerefentry project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
  81     for more information on the various clocks. The retrieved
  82     timestamp is stored in the <parameter>usec</parameter> parameter,
  83     in µs since the clock's epoch. If this function is invoked before
  84     the first event loop iteration, the current time is returned, as
  85     reported by <function>clock_gettime()</function>. To distinguish
  86     this case from a regular invocation the return value will be
  87     positive, and zero when the returned timestamp refers to an actual
  88     event loop iteration.</para>
  89   </refsect1>
  90
  91   <refsect1>
  92     <title>Return Value</title>
  93
  94     <para>If the first event loop iteration has not run yet
  95     <function>sd_event_now()</function> writes current time to
  96     <parameter>usec</parameter> and returns a positive return value.
  97     Otherwise, it will write the requested timestamp to <parameter>usec</parameter>
  98     and return 0. On failure, the call returns a negative errno-style
  99     error code.</para>
 100   </refsect1>
 101
 102   <refsect1>
 103     <title>Errors</title>
 104
 105     <para>Returned values may indicate the following problems:</para>
 106
 107     <variablelist>
 108       <varlistentry>
 109         <term><constant>-EINVAL</constant></term>
 110
 111         <listitem><para>An invalid parameter was
 112         passed.</para></listitem>
 113
 114       </varlistentry>
 115
 116       <varlistentry>
 117         <term><constant>-EOPNOTSUPP</constant></term>
 118
 119         <listitem><para>Unsupported clock type.
 120         </para></listitem>
 121       </varlistentry>
 122
 123       <varlistentry>
 124         <term><constant>-ECHILD</constant></term>
 125
 126         <listitem><para>The event loop object was created in a
 127         different process.</para></listitem>
 128       </varlistentry>
 129     </variablelist>
 130   </refsect1>
 131
 132   <xi:include href="libsystemd-pkgconfig.xml" />
 133
 134   <refsect1>
 135     <title>See Also</title>
 136
 137     <para>
 138       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 139       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 140       <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 141       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 142       <citerefentry project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 143     </para>
 144   </refsect1>
 145
 146 </refentry>