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systemd/man/sd_event_now.xml
Zbigniew Jędrzejewski-Szmek 11a1589223 tree-wide: drop license boilerplate
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.

I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
2018-04-06 18:58:55 +02:00

136 lines
4.6 KiB
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_now" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_event_now</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_now</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_event_now</refname>
<refpurpose>Retrieve current event loop iteration timestamp</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_event_now</function></funcdef>
<paramdef>sd_event *<parameter>event</parameter></paramdef>
<paramdef>clockid_t <parameter>clock</parameter></paramdef>
<paramdef>uint64_t *<parameter>usec</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_event_now()</function> returns the time when
the most recent event loop iteration began. A timestamp
is taken right after returning from the event sleep, and before
dispatching any event sources. The <parameter>event</parameter>
parameter specifies the event loop object to retrieve the timestamp
from. The <parameter>clock</parameter> parameter specifies the clock to
retrieve the timestamp for, and is one of
<constant>CLOCK_REALTIME</constant> (or equivalently
<constant>CLOCK_REALTIME_ALARM</constant>),
<constant>CLOCK_MONOTONIC</constant>, or
<constant>CLOCK_BOOTTIME</constant> (or equivalently
<constant>CLOCK_BOOTTIME_ALARM</constant>), see
<citerefentry project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
for more information on the various clocks. The retrieved
timestamp is stored in the <parameter>usec</parameter> parameter,
in µs since the clock's epoch. If this function is invoked before
the first event loop iteration, the current time is returned, as
reported by <function>clock_gettime()</function>. To distinguish
this case from a regular invocation the return value will be
positive, and zero when the returned timestamp refers to an actual
event loop iteration.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>If the first event loop iteration has not run yet
<function>sd_event_now()</function> writes current time to
<parameter>usec</parameter> and returns a positive return value.
Otherwise, it will write the requested timestamp to <parameter>usec</parameter>
and return 0. On failure, the call returns a negative errno-style
error code.</para>
</refsect1>
<refsect1>
<title>Errors</title>
<para>Returned values may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><constant>-EINVAL</constant></term>
<listitem><para>An invalid parameter was
passed.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-EOPNOTSUPP</constant></term>
<listitem><para>Unsupported clock type.
</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ECHILD</constant></term>
<listitem><para>The event loop object was created in a
different process.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>