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authorLennart Poettering <lennart@poettering.net>2014-05-06 18:51:08 +0200
committerLennart Poettering <lennart@poettering.net>2014-05-06 18:51:08 +0200
commitb408026b9899c1f9d155ac6d9f7bdc7f5cd3defb (patch)
tree415dbf64c37e17e71ecd0987b1ffac3d5edd9a98 /man/sd_event_add_time.xml
parent7b8b9686e050a2b19ed2a3686af187dffaab5c08 (diff)
man: document sd_event_add_time(3)
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+<?xml version='1.0'?> <!--*-nxml-*-->
+<!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 2014 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_add_time" conditional="ENABLE_KDBUS">
+
+ <refentryinfo>
+ <title>sd_event_add_time</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_add_time</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_event_add_time</refname>
+ <refname>sd_event_source_get_time</refname>
+ <refname>sd_event_source_set_time</refname>
+ <refname>sd_event_source_get_time_accuracy</refname>
+ <refname>sd_event_source_set_time_accuracy</refname>
+ <refname>sd_event_source_get_time_clock</refname>
+
+ <refpurpose>Add a timer event source to an event loop</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_add_time</function></funcdef>
+ <paramdef>sd_event *<parameter>event</parameter></paramdef>
+ <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
+ <paramdef>clockid_t <parameter>clock</parameter></paramdef>
+ <paramdef>uint64_t <parameter>usec</parameter></paramdef>
+ <paramdef>uint64_t <parameter>accuracy</parameter></paramdef>
+ <paramdef>sd_event_time_handler_t <parameter>handler</parameter></paramdef>
+ <paramdef>void* <parameter>userdata</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_get_time</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>usec_t* <parameter>usec</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_set_time</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>usec_t <parameter>usec</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_get_time_accuracy</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>usec_t *<parameter>usec</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_set_time_accuracy</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>usec_t <parameter>usec</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_get_time_clock</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>clockid_t *<parameter>clock</parameter></paramdef>
+ </funcprototype>
+
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_event_add_time()</function> adds a new timer
+ event source to an event loop object. The event loop is specified
+ in <parameter>event</parameter>, the event source is returned in
+ the <parameter>source</parameter> parameter. The
+ <parameter>clock</parameter> parameter takes a clock identifier,
+ one of <constant>CLOCK_REALTIME</constant>,
+ <constant>CLOCK_MONOTONIC</constant> and
+ <constant>CLOCK_BOOTTIME_ALARM</constant>. See
+ <citerefentry><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ for details regarding the various types of clocks. The
+ <parameter>usec</parameter> parameter takes a time value in
+ microseconds, relative to the clock's epoch specifying when the
+ timer shall elapse the earliest. The
+ <parameter>accuracy</parameter> parameter takes an additional
+ accuracy value in microseconds specifying a time the timer event
+ may be delayed. Specify 0 for selecting the default accuracy
+ (250ms). Specify 1 for most accurate timers. Consider specifying
+ 60000000 or larger (1h) for long running events that may be
+ delayed substantially. Picking higher accuracy values allows the
+ system to coalesce timer events more aggressively, thus improving
+ power efficiency. The <parameter>handler</parameter> shall
+ reference a function to call when the timer elapses. The handler
+ function will be passed the <parameter>userdata</parameter>
+ pointer, which may be chosen freely by the caller. The handler is
+ also passed the configured time it was triggered, however it might
+ actually have been called at a slightly later time, subject to the
+ specified accuracy value, the kernel timer slack (see
+ <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>)
+ and additional scheduling latencies. By default the timer will
+ elapse once (SD_EVENT_ONESHOT), but this may be changed with
+ <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
+ the handler function returns a negative error code it will be
+ disabled after the invocation, even if SD_EVENT_ON mode is set.
+ </para>
+
+ <para><function>sd_event_source_get_time()</function> retrieves
+ the configured time value of a timer event source created
+ previously with <function>sd_event_add_time()</function>. It takes
+ the event source object and a pointer to a variable to store the
+ time in microseconds in.</para>
+
+ <para><function>sd_event_source_set_time()</function> changes the
+ configured time value of a timer event source created previously
+ with <function>sd_event_add_time()</function>. It takes the event
+ source object and a time relative to the selected clock's
+ epoch, in microseconds.</para>
+
+ <para><function>sd_event_source_get_time_accuracy()</function>
+ retrieves the configured accuracy value of a timer event source
+ created previously with <function>sd_event_add_time()</function>. It
+ takes the event source object and a pointer to a variable to store
+ the accuracy in microseconds in.</para>
+
+ <para><function>sd_event_source_set_time_accuracy()</function>
+ changes the configured accuracy of a timer event source created
+ previously with <function>sd_event_add_time()</function>. It takes
+ the event source object and an accuracy, in microseconds.</para>
+
+ <para><function>sd_event_source_get_time_clock()</function>
+ retrieves the configured clock of a timer event source created
+ previously with <function>sd_event_add_time()</function>. It takes
+ the event source object and a pointer to a variable to store the
+ clock identifier in.</para>
+
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>On success, these functions return 0 or a positive
+ integer. On failure, they return a negative errno-style error
+ code. </para>
+ </refsect1>
+
+ <refsect1>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><varname>-ENOMEM</varname></term>
+
+ <listitem><para>Not enough memory to allocate object.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>-EINVAL</varname></term>
+
+ <listitem><para>An invalid argument has been passed.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>-ESTALE</varname></term>
+
+ <listitem><para>The event loop is already terminated.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>-ECHILD</varname></term>
+
+ <listitem><para>The event loop has been created in a different process.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>-ENOTSUP</varname></term>
+
+ <listitem><para>The selected clock is not supported by the event loop implementation.</para></listitem>
+
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <para><function>sd_event_add_time()</function> and the other functions
+ described here are available as a shared library, which can be
+ compiled and linked to with the
+ <constant>libsystemd</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ file.</para>
+ </refsect1>
+
+ <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>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>