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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 <systemd/sd-bus.h></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>
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