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0N/A"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

0N/A

0N/A

0N/A<refentry id="sd_event_add_time" xmlns:xi="http://www.w3.org/2001/XInclude">

0N/A

0N/A <refentryinfo>

0N/A <title>sd_event_add_time</title>

0N/A <productname>systemd</productname>

0N/A

0N/A <authorgroup>

0N/A <author>

0N/A <contrib>Developer</contrib>

0N/A <firstname>Lennart</firstname>

0N/A <surname>Poettering</surname>

0N/A <email>lennart@poettering.net</email>

0N/A </author>

0N/A </authorgroup>

0N/A </refentryinfo>

0N/A

0N/A <refmeta>

0N/A <refentrytitle>sd_event_add_time</refentrytitle>

0N/A <manvolnum>3</manvolnum>

0N/A </refmeta>

0N/A

0N/A <refnamediv>

0N/A <refname>sd_event_add_time</refname>

0N/A <refname>sd_event_source_get_time</refname>

0N/A <refname>sd_event_source_set_time</refname>

0N/A <refname>sd_event_source_get_time_accuracy</refname>

0N/A <refname>sd_event_source_set_time_accuracy</refname>

0N/A <refname>sd_event_source_get_time_clock</refname>

0N/A <refname>sd_event_time_handler_t</refname>

169N/A

0N/A <refpurpose>Add a timer event source to an event loop</refpurpose>

0N/A </refnamediv>

169N/A

0N/A <refsynopsisdiv>

169N/A <funcsynopsis>

169N/A <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>

169N/A

169N/A <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo>

169N/A

169N/A <funcprototype>

169N/A <funcdef>typedef int (*<function>sd_event_time_handler_t</function>)</funcdef>

169N/A <paramdef>sd_event_source *<parameter>s</parameter></paramdef>

169N/A <paramdef>uint64_t <parameter>usec</parameter></paramdef>

169N/A <paramdef>void *<parameter>userdata</parameter></paramdef>

169N/A </funcprototype>

0N/A

169N/A <funcprototype>

169N/A <funcdef>int <function>sd_event_add_time</function></funcdef>

0N/A <paramdef>sd_event *<parameter>event</parameter></paramdef>

169N/A <paramdef>sd_event_source **<parameter>source</parameter></paramdef>

169N/A <paramdef>clockid_t <parameter>clock</parameter></paramdef>

169N/A <paramdef>uint64_t <parameter>usec</parameter></paramdef>

169N/A <paramdef>uint64_t <parameter>accuracy</parameter></paramdef>

169N/A <paramdef>sd_event_time_handler_t <parameter>handler</parameter></paramdef>

169N/A <paramdef>void *<parameter>userdata</parameter></paramdef>

0N/A </funcprototype>

169N/A

169N/A <funcprototype>

169N/A <funcdef>int <function>sd_event_source_get_time</function></funcdef>

0N/A <paramdef>sd_event_source *<parameter>source</parameter></paramdef>

169N/A <paramdef>uint64_t *<parameter>usec</parameter></paramdef>

169N/A </funcprototype>

169N/A

169N/A <funcprototype>

169N/A <funcdef>int <function>sd_event_source_set_time</function></funcdef>

169N/A <paramdef>sd_event_source *<parameter>source</parameter></paramdef>

0N/A <paramdef>uint64_t <parameter>usec</parameter></paramdef>

169N/A </funcprototype>

169N/A

169N/A <funcprototype>

0N/A <funcdef>int <function>sd_event_source_get_time_accuracy</function></funcdef>

169N/A <paramdef>sd_event_source *<parameter>source</parameter></paramdef>

169N/A <paramdef>uint64_t *<parameter>usec</parameter></paramdef>

169N/A </funcprototype>

169N/A

169N/A <funcprototype>

169N/A <funcdef>int <function>sd_event_source_set_time_accuracy</function></funcdef>

169N/A <paramdef>sd_event_source *<parameter>source</parameter></paramdef>

0N/A <paramdef>uint64_t <parameter>usec</parameter></paramdef>

169N/A </funcprototype>

169N/A

169N/A <funcprototype>

169N/A <funcdef>int <function>sd_event_source_get_time_clock</function></funcdef>

169N/A <paramdef>sd_event_source *<parameter>source</parameter></paramdef>

0N/A <paramdef>clockid_t *<parameter>clock</parameter></paramdef>

169N/A </funcprototype>

169N/A

169N/A </funcsynopsis>

169N/A </refsynopsisdiv>

169N/A

169N/A <refsect1>

169N/A <title>Description</title>

169N/A

0N/A <para><function>sd_event_add_time()</function> adds a new timer

169N/A event source to an event loop. The event loop object is specified

0N/A in the <parameter>event</parameter> parameter, the event source

0N/A object is returned in the <parameter>source</parameter>

0N/A parameter. The <parameter>clock</parameter> parameter takes a

169N/A clock identifier, one of <constant>CLOCK_REALTIME</constant>,

0N/A <constant>CLOCK_MONOTONIC</constant>,

169N/A <constant>CLOCK_BOOTTIME</constant>,

0N/A <constant>CLOCK_REALTIME_ALARM</constant> or

169N/A <constant>CLOCK_BOOTTIME_ALARM</constant>. See

169N/A <citerefentry><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>

169N/A for details regarding the various types of clocks. The

169N/A <parameter>usec</parameter> parameter takes a time value in

169N/A microseconds (µs), relative to the clock's epoch, specifying when

0N/A the timer shall elapse the earliest. If a time that already lies

169N/A in the past is specified (including 0), the timer source is

169N/A dispatched immediately in the next event loop iterations. The

169N/A <parameter>accuracy</parameter> parameter takes an additional

169N/A accuracy value in µs specifying a time the timer event may be

169N/A delayed. Specify 0 for selecting the default accuracy

169N/A (250ms). Specify 1µs for most accurate timers. Consider specifying

169N/A 60000000µs or larger (1min) for long-running events that may be

169N/A delayed substantially. Picking higher accuracy values allows the

169N/A system to coalesce timer events more aggressively, thus improving

169N/A power efficiency. The <parameter>handler</parameter> parameter

169N/A shall reference a function to call when the timer elapses. The

169N/A handler function will be passed the

169N/A <parameter>userdata</parameter> pointer, which may be chosen

169N/A freely by the caller. The handler is also passed the configured

169N/A time it was triggered, however it might actually have been called

169N/A at a slightly later time, subject to the specified accuracy value,

169N/A the kernel timer slack (see

169N/A <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>)

169N/A and additional scheduling latencies. To query the actual time the

0N/A handler was called use

169N/A <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>

169N/A

169N/A <para>By default, the timer will elapse once

169N/A (<constant>SD_EVENT_ONESHOT</constant>), but this may be changed

169N/A with

169N/A <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.

0N/A If the handler function returns a negative error code, it will be

0N/A disabled after the invocation, even if the

0N/A <constant>SD_EVENT_ON</constant> mode was requested before. Note

169N/A that a timer event set to <constant>SD_EVENT_ON</constant> will

169N/A fire continously unless its configured time is updated using

0N/A <function>sd_event_source_set_time()</function>.

169N/A </para>

169N/A

169N/A <para>To destroy an event source object use

169N/A <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

169N/A but note that the event source is only removed from the event loop

169N/A when all references to the event source are dropped. To make sure

0N/A an event source does not fire anymore, even when there's still a

169N/A reference to it kept, consider setting the event source to

169N/A <constant>SD_EVENT_OFF</constant> with

169N/A <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>

169N/A

169N/A <para>If the the second parameter of

169N/A <function>sd_event_add_time()</function> is passed as NULL no

0N/A reference to the event source object is returned. In this case the

169N/A event source is considered "floating", and will be destroyed

169N/A implicitly when the event loop itself is destroyed.</para>

169N/A

169N/A <para>If the <parameter>handler</parameter> to

0N/A <function>sd_event_add_time()</function> is passed as NULL, and

0N/A the event source fires, this will be considered a request to exit

the event loop. In this case, the <parameter>userdata</parameter>

parameter, cast to an integer is used for the exit code passed to

<citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>

<para>Use <constant>CLOCK_BOOTTIME_ALARM</constant> and

<constant>CLOCK_REALTIME_ALARM</constant> to define event sources

that may wake up the system from suspend.</para>

<para>In order to set up relative timers (that is, relative to the

current time), retrieve the current time via

<citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

add the desired timespan to sleep to it, and pass the result as

the <parameter>usec</parameter> parameter to

<function>sd_event_add_time()</function>.</para>

<para>In order to set up repetitive timers (that is, timers that

are triggered in regular intervals), set up the timer normally,

for the first invocation. Each time the event handler is invoked,

update the timer's trigger time with

<citerefentry><refentrytitle>sd_event_source_set_time</refentrytitle><manvolnum>3</manvolnum></citerefentry> for the next timer

iteration, and reenable the timer using

<function>sd_event_source_set_enabled()</function>. To calculate

the next point in time to pass to

<function>sd_event_source_set_time()</function>, either use as

base the <parameter>usec</parameter> parameter passed to the timer

callback, or the timestamp returned by

<function>sd_event_now()</function>. In the former case timer

events will be regular, while in the latter case the scheduling

latency will keep accumulating on the timer.</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, relative to the selected clock's epoch, in µs 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 µs.</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 µs 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 µs.</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>

<varlistentry>

<term><constant>-EDOM</constant></term>

<listitem><para>The passed event source is not a timer event source.</para></listitem>

</varlistentry>

</variablelist>

</refsect1>

<xi:include href="libsystemd-pkgconfig.xml" />

<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_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

<citerefentry><refentrytitle>sd_event_add_io</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>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

<citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

<citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

<citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

<citerefentry project='man-pages'><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>,

<citerefentry project='man-pages'><refentrytitle>timerfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>,

<citerefentry project='man-pages'><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>

</para>

</refsect1>

</refentry>