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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 219</span><hr><div class="refentry"><a name="sd_watchdog_enabled"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_watchdog_enabled — Check whether the service manager expects watchdog keep-alive notifications from a service</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <systemd/sd-daemon.h></pre><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_watchdog_enabled</b>(</code></td><td>int <var class="pdparam">unset_environment</var>, </td></tr><tr><td> </td><td>uint64_t *<var class="pdparam">usec</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm139948475415984"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_watchdog_enabled()</code> may be called by
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a service to detect whether the service manager expects regular
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keep-alive watchdog notification events from it, and the timeout
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after which the manager will act on the service if it did not get
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such a notification.</p><p>If the <code class="varname">$WATCHDOG_USEC</code> environment
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variable is set, and the <code class="varname">$WATCHDOG_PID</code> variable
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is unset or set to the PID of the current process, the service
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manager expects notifications from this process. The manager will
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usually terminate a service when it does not get a notification
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message within the specified time after startup and after each
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previous message. It is recommended that a daemon sends a
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keep-alive notification message to the service manager every half
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of the time returned here. Notification messages may be sent with
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<a href="sd_notify.html"><span class="citerefentry"><span class="refentrytitle">sd_notify</span>(3)</span></a>
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with a message string of "<code class="literal">WATCHDOG=1</code>".</p><p>If the <em class="parameter"><code>unset_environment</code></em> parameter is
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non-zero, <code class="function">sd_watchdog_enabled()</code> will unset
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the <code class="varname">$WATCHDOG_USEC</code> and
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<code class="varname">$WATCHDOG_PID</code> environment variables before
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returning (regardless of whether the function call itself
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succeeded or not). Those variables are no longer inherited by
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child processes. Further calls to
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<code class="function">sd_watchdog_enabled()</code> will also return with
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zero.</p><p>If the <em class="parameter"><code>usec</code></em> parameter is non-NULL,
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<code class="function">sd_watchdog_enabled()</code> will write the timeout
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in µs for the watchdog logic to it.</p><p>To enable service supervision with the watchdog logic, use
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<code class="varname">WatchdogSec=</code> in service files. See
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<a href="systemd.service.html"><span class="citerefentry"><span class="refentrytitle">systemd.service</span>(5)</span></a>
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for details.</p></div><div class="refsect1"><a name="idm139948479301664"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p>On failure, this call returns a negative errno-style error
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code. If the service manager expects watchdog keep-alive
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notification messages to be sent, > 0 is returned, otherwise 0
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is returned. Only if the return value is > 0, the
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<em class="parameter"><code>usec</code></em> parameter is valid after the
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call.</p></div><div class="refsect1"><a name="idm139948479299408"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p><a name="pkgconfig-text"></a>These APIs are implemented as a shared
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library, which can be compiled and linked to with the
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<code class="constant">libsystemd</code> <a href="http://linux.die.net/man/1/pkg-config"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
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file.</p><p>Internally, this functions parses the
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<code class="varname">$WATCHDOG_PID</code> and
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<code class="varname">$WATCHDOG_USEC</code> environment variable. The call
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will ignore these variables if <code class="varname">$WATCHDOG_PID</code>
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does not contain the PID of the current process, under the
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assumption that in that case, the variables were set for a
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different process further up the process tree.</p></div><div class="refsect1"><a name="idm139948479295840"></a><h2 id="Environment">Environment<a class="headerlink" title="Permalink to this headline" href="#Environment">¶</a></h2><div class="variablelist"><dl class="variablelist"><dt id="$WATCHDOG_PID"><span class="term"><code class="varname">$WATCHDOG_PID</code></span><a class="headerlink" title="Permalink to this term" href="#%24WATCHDOG_PID">¶</a></dt><dd><p>Set by the system manager for supervised
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process for which watchdog support is enabled, and contains
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the PID of that process. See above for
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details.</p></dd><dt id="$WATCHDOG_USEC"><span class="term"><code class="varname">$WATCHDOG_USEC</code></span><a class="headerlink" title="Permalink to this term" href="#%24WATCHDOG_USEC">¶</a></dt><dd><p>Set by the system manager for supervised
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process for which watchdog support is enabled, and contains
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the watchdog timeout in µs See above for
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details.</p></dd></dl></div></div><div class="refsect1"><a name="idm139948479290944"></a><h2 id="History">History<a class="headerlink" title="Permalink to this headline" href="#History">¶</a></h2><p>The watchdog functionality and the
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<code class="varname">$WATCHDOG_USEC</code> variable were added in
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systemd-41.</p><p><code class="function">sd_watchdog_enabled()</code> function was
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added in systemd-209. Since that version the
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<code class="varname">$WATCHDOG_PID</code> variable is also set.</p></div><div class="refsect1"><a name="idm139948479287856"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
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<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
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<a href="sd-daemon.html"><span class="citerefentry"><span class="refentrytitle">sd-daemon</span>(3)</span></a>,
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<a href="daemon.html"><span class="citerefentry"><span class="refentrytitle">daemon</span>(7)</span></a>,
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<a href="systemd.service.html"><span class="citerefentry"><span class="refentrytitle">systemd.service</span>(5)</span></a>,
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<a href="sd_notify.html"><span class="citerefentry"><span class="refentrytitle">sd_notify</span>(3)</span></a>
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</p></div></div></body></html>
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