| <?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> |