<?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 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"> <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>typedef int (*<function>sd_event_time_handler_t</function>)</funcdef> <paramdef>sd_event_source *<parameter>s</parameter></paramdef> <paramdef>uint64_t <parameter>usec</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.</para> <para>By default, the timer will elapse once (<constant>SD_EVENT_ONESHOT</constant>), 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 <constant>SD_EVENT_ON</constant> 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><constant>-ENOMEM</constant></term> <listitem><para>Not enough memory to allocate an object.</para></listitem> </varlistentry> <varlistentry> <term><constant>-EINVAL</constant></term> <listitem><para>An invalid argument has been passed.</para></listitem> </varlistentry> <varlistentry> <term><constant>-ESTALE</constant></term> <listitem><para>The event loop is already terminated.</para></listitem> </varlistentry> <varlistentry> <term><constant>-ECHILD</constant></term> <listitem><para>The event loop has been created in a different process.</para></listitem> </varlistentry> <varlistentry> <term><constant>-EOPNOTSUPP</constant></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 project='die-net'><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>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd_event_add_defer</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>