"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
+ SPDX-License-Identifier: LGPL-2.1+
+
This file is part of systemd.
Copyright 2014 Lennart Poettering
<refsect1>
<title>Description</title>
- <para><function>sd_event_add_time()</function> adds a new timer
- event source to an event loop. The event loop object is specified
- in the <parameter>event</parameter> parameter, the event source
- object 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>,
- <constant>CLOCK_BOOTTIME</constant>,
- <constant>CLOCK_REALTIME_ALARM</constant>, or
- <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 specifies the earliest time,
- in microseconds (µs), relative to the clock's epoch, when
- the timer shall be triggered. If a time already in the past is
- specified (including <constant>0</constant>), this timer source
- "fires" immediately and is ready to be dispatched. The
- <parameter>accuracy</parameter> parameter specifies an additional
- accuracy value in µs specifying how much the timer event may be
- delayed. Use <constant>0</constant> to select the default accuracy
- (250ms). Use 1µs for maximum accuracy. Consider specifying
- 60000000µs (1min) or larger for long-running events that may be
- delayed substantially. Picking higher accuracy values allows the
- system to coalesce timer events more aggressively, improving
- power efficiency. The <parameter>handler</parameter> 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
- trigger time, even if it is actually called
- slightly later, subject to the specified accuracy value,
- the kernel timer slack (see
- <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>),
- and additional scheduling latencies. To query the actual time the
- handler was called use
+ <para><function>sd_event_add_time()</function> adds a new timer event source to an event loop. The event loop
+ object is specified in the <parameter>event</parameter> parameter, the event source object 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>, <constant>CLOCK_BOOTTIME</constant>,
+ <constant>CLOCK_REALTIME_ALARM</constant>, or <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 specifies the earliest time, in
+ microseconds (µs), relative to the clock's epoch, when the timer shall be triggered. If a time already in the past
+ is specified (including <constant>0</constant>), this timer source "fires" immediately and is ready to be
+ dispatched. If the parameter is specified as <constant>UINT64_MAX</constant> the timer event will never elapse,
+ which may be used as an alternative to explicitly disabling a timer event source with
+ <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. The
+ <parameter>accuracy</parameter> parameter specifies an additional accuracy value in µs specifying how much the
+ timer event may be delayed. Use <constant>0</constant> to select the default accuracy (250ms). Use 1µs for maximum
+ accuracy. Consider specifying 60000000µs (1min) or larger for long-running events that may be delayed
+ substantially. Picking higher accuracy values allows the system to coalesce timer events more aggressively,
+ improving power efficiency. The <parameter>handler</parameter> 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 trigger time, even if it is actually called
+ slightly later, subject to the specified accuracy value, the kernel timer slack (see
+ <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>), and additional
+ scheduling latencies. To query the actual time the handler was called use
<citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
<para>By default, the timer will elapse once
in µs.</para>
<para><function>sd_event_source_get_time_accuracy()</function>
- retrieves the configured accuracy value of a event source
+ retrieves the configured accuracy value of an 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. The accuracy is specified in µs.</para>
the event source object and accuracy, in µs.</para>
<para><function>sd_event_source_get_time_clock()</function>
- retrieves the configured clock of a event source created
+ retrieves the configured clock of an 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>
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