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authorLennart Poettering <lennart@poettering.net>2015-11-19 23:38:54 +0100
committerLennart Poettering <lennart@poettering.net>2015-11-19 23:38:54 +0100
commitdc83f27a7cf03757dec11a69ec18504ad4ea8f89 (patch)
tree54af47fe95cdaa44ea4f0e3c0c3482e40c46edc3 /man/sd_event_now.xml
parent0be6c2f617732902921d42bb0705f016b2838aba (diff)
man: fully document sd-event interfaces
This completes the set of man pages for sd-event and contains some minor other fixes for other man pages too. The sd_event_set_name(3) man page is renamed to sd_event_source_set_description(3), which is the correct name of the concept today.
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+<?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">
+
+<!--
+ This file is part of systemd.
+
+ Copyright 2015 Lennart Poettering
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<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 timestamp
+ the most recent event loop iteration began. This timestamp is
+ taken right after after returning from the event sleep, and before
+ dispatching any event sources. The <parameter>event</parameter>
+ parameter takes the even 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 its equivalent
+ <constant>CLOCK_REALTIME_ALARM</constant>),
+ <constant>CLOCK_MONOTONIC</constant> or
+ <constant>CLOCK_BOOTTIME</constant> (or its equivalent
+ <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 non-zero in this case, while it is zero when the returned
+ timestamp refers to the 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> returns the requested
+ timestamp in <parameter>usec</parameter> and returns a positive,
+ non-zero return value. Otherwise, on success it will return the
+ iteration's timestamp in <parameter>usec</parameter> and 0 as
+ return value. On failure, the call returns a negative errno-style
+ error code.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Errors</title>
+
+ <para>Returned errors 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>-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>