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+<?xml version='1.0'?> <!--*-nxml-*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
+
+<refentry id="sd_watchdog_enabled"
+ xmlns:xi="http://www.w3.org/2001/XInclude">
+
+ <refentryinfo>
+ <title>sd_watchdog_enabled</title>
+ <productname>systemd</productname>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>sd_watchdog_enabled</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_watchdog_enabled</refname>
+ <refpurpose>Check whether the service manager expects watchdog keep-alive notifications from a service</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include &lt;systemd/sd-daemon.h&gt;</funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_watchdog_enabled</function></funcdef>
+ <paramdef>int <parameter>unset_environment</parameter></paramdef>
+ <paramdef>uint64_t *<parameter>usec</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+ <para><function>sd_watchdog_enabled()</function> may be called by
+ a service to detect whether the service manager expects regular
+ keep-alive watchdog notification events from it, and the timeout
+ after which the manager will act on the service if it did not get
+ such a notification.</para>
+
+ <para>If the <varname>$WATCHDOG_USEC</varname> environment
+ variable is set, and the <varname>$WATCHDOG_PID</varname> variable
+ is unset or set to the PID of the current process, the service
+ manager expects notifications from this process. The manager will
+ usually terminate a service when it does not get a notification
+ message within the specified time after startup and after each
+ previous message. It is recommended that a daemon sends a
+ keep-alive notification message to the service manager every half
+ of the time returned here. Notification messages may be sent with
+ <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ with a message string of <literal>WATCHDOG=1</literal>.</para>
+
+ <para>If the <parameter>unset_environment</parameter> parameter is
+ non-zero, <function>sd_watchdog_enabled()</function> will unset
+ the <varname>$WATCHDOG_USEC</varname> and
+ <varname>$WATCHDOG_PID</varname> environment variables before
+ returning (regardless of whether the function call itself
+ succeeded or not). Those variables are no longer inherited by
+ child processes. Further calls to
+ <function>sd_watchdog_enabled()</function> will also return with
+ zero.</para>
+
+ <para>If the <parameter>usec</parameter> parameter is non-<constant>NULL</constant>,
+ <function>sd_watchdog_enabled()</function> will write the timeout
+ in µs for the watchdog logic to it.</para>
+
+ <para>To enable service supervision with the watchdog logic, use
+ <varname>WatchdogSec=</varname> in service files. See
+ <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for details.</para>
+
+ <para>Use
+ <citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ to enable automatic watchdog support in
+ <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>-based event loops.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>On failure, this call returns a negative errno-style error
+ code. If the service manager expects watchdog keep-alive
+ notification messages to be sent, &gt; 0 is returned, otherwise 0
+ is returned. Only if the return value is &gt; 0, the
+ <parameter>usec</parameter> parameter is valid after the
+ call.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
+
+ <para>Internally, this function parses the
+ <varname>$WATCHDOG_PID</varname> and
+ <varname>$WATCHDOG_USEC</varname> environment variable. The call
+ will ignore these variables if <varname>$WATCHDOG_PID</varname>
+ does not contain the PID of the current process, under the
+ assumption that in that case, the variables were set for a
+ different process further up the process tree.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Environment</title>
+
+ <variablelist class='environment-variables'>
+ <varlistentry>
+ <term><varname>$WATCHDOG_PID</varname></term>
+
+ <listitem><para>Set by the system manager for supervised
+ process for which watchdog support is enabled, and contains
+ the PID of that process. See above for
+ details.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$WATCHDOG_USEC</varname></term>
+
+ <listitem><para>Set by the system manager for supervised
+ process for which watchdog support is enabled, and contains
+ the watchdog timeout in µs. See above for
+ details.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_set_watchdog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>