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  <a href="../libudev/index.html">gudev </a><span style="float:right">systemd 215</span><hr><div class="refentry"><a name="sd_notify"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_notify, sd_notifyf — Notify service manager about start-up completion and other daemon status changes</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include &lt;systemd/sd-daemon.h&gt;</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_notify</b>(</code></td><td>int <var class="pdparam">unset_environment</var>, </td></tr><tr><td> </td><td>const char *<var class="pdparam">state</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_notifyf</b>(</code></td><td>int <var class="pdparam">unset_environment</var>, </td></tr><tr><td> </td><td>const char *<var class="pdparam">format</var>, </td></tr><tr><td> </td><td>...<code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm214198380880"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description"></a></h2><p><code class="function">sd_notify()</code> shall be called
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                by a daemon to notify the init system about status
                changes. It can be used to send arbitrary information,
                encoded in an environment-block-like string. Most
                importantly it can be used for start-up completion
                notification.</p><p>If the <em class="parameter"><code>unset_environment</code></em>
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                parameter is non-zero, <code class="function">sd_notify()</code>
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                will unset the <code class="varname">$NOTIFY_SOCKET</code>
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                environment variable before returning (regardless of
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                whether the function call itself succeeded or
                not). Further calls to
                <code class="function">sd_notify()</code> will then fail, but
                the variable is no longer inherited by child
                processes.</p><p>The <em class="parameter"><code>state</code></em> parameter
                should contain a newline-separated list of variable
                assignments, similar in style to an environment
                block. A trailing newline is implied if none is
                specified. The string may contain any kind of variable
                assignments, but the following shall be considered
                well-known:</p><div class="variablelist"><dl class="variablelist"><dt id="READY=1"><span class="term">READY=1</span><a class="headerlink" title="Permalink to this term" href="#READY=1"></a></dt><dd><p>Tells the init system
                                that daemon startup is finished. This
                                is only used by systemd if the service
                                definition file has Type=notify
                                set. The passed argument is a boolean
                                "1" or "0". Since there is little
                                value in signaling non-readiness, the
                                only value daemons should send is
                                "READY=1".</p></dd><dt id="STATUS=..."><span class="term">STATUS=...</span><a class="headerlink" title="Permalink to this term" href="#STATUS=..."></a></dt><dd><p>Passes a single-line
                                status string back to the init system
                                that describes the daemon state. This
                                is free-form and can be used for
                                various purposes: general state
                                feedback, fsck-like programs could
                                pass completion percentages and
                                failing programs could pass a human
                                readable error message. Example:
                                "STATUS=Completed 66% of file system
                                check..."</p></dd><dt id="ERRNO=..."><span class="term">ERRNO=...</span><a class="headerlink" title="Permalink to this term" href="#ERRNO=..."></a></dt><dd><p>If a daemon fails, the
                                errno-style error code, formatted as
                                string. Example: "ERRNO=2" for
                                ENOENT.</p></dd><dt id="BUSERROR=..."><span class="term">BUSERROR=...</span><a class="headerlink" title="Permalink to this term" href="#BUSERROR=..."></a></dt><dd><p>If a daemon fails, the
                                D-Bus error-style error code. Example:
                                "BUSERROR=org.freedesktop.DBus.Error.TimedOut"</p></dd><dt id="MAINPID=..."><span class="term">MAINPID=...</span><a class="headerlink" title="Permalink to this term" href="#MAINPID=..."></a></dt><dd><p>The main pid of the
                                daemon, in case the init system did
                                not fork off the process
                                itself. Example:
                                "MAINPID=4711"</p></dd><dt id="WATCHDOG=1"><span class="term">WATCHDOG=1</span><a class="headerlink" title="Permalink to this term" href="#WATCHDOG=1"></a></dt><dd><p>Tells systemd to
                                update the watchdog timestamp. This is
                                the keep-alive ping that services need
                                to issue in regular intervals if
                                <code class="varname">WatchdogSec=</code> is
                                enabled for it. See
                                <a href="systemd.service.html"><span class="citerefentry"><span class="refentrytitle">systemd.service</span>(5)</span></a>
                                for details. It is recommended to send
                                this message if the
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                                <code class="varname">$WATCHDOG_PID</code>
                                environment variable has been set to
                                the PID of the service process, in
                                every half the time interval that is
                                specified in the
                                <code class="varname">$WATCHDOG_USEC</code>
                                environment variable. See
                                <a href="sd_watchdog_enabled.html"><span class="citerefentry"><span class="refentrytitle">sd_watchdog_enabled</span>(3)</span></a>
                                for details.</p></dd></dl></div><p>It is recommended to prefix variable names that
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                are not shown in the list above with
                <code class="varname">X_</code> to avoid namespace
                clashes.</p><p>Note that systemd will accept status data sent
                from a daemon only if the
                <code class="varname">NotifyAccess=</code> option is correctly
                set in the service definition file. See
                <a href="systemd.service.html"><span class="citerefentry"><span class="refentrytitle">systemd.service</span>(5)</span></a>
                for details.</p><p><code class="function">sd_notifyf()</code> is similar to
                <code class="function">sd_notify()</code> but takes a
                <code class="function">printf()</code>-like format string plus
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                arguments.</p></div><div class="refsect1"><a name="idm214198431088"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value"></a></h2><p>On failure, these calls return a negative
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                errno-style error code. If
                <code class="varname">$NOTIFY_SOCKET</code> was not set and
                hence no status data could be sent, 0 is returned. If
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                the status was sent, these functions return with a
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                positive return value. In order to support both, init
                systems that implement this scheme and those which
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                do not, it is generally recommended to ignore the return
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                value of this call.</p></div><div class="refsect1"><a name="idm214198428960"></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
  <code class="constant">libsystemd</code> <a href="pkg-config.html"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
  file.</p><p>Internally, these functions send a single
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                datagram with the state string as payload to the
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                <code class="constant">AF_UNIX</code> socket referenced in the
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                <code class="varname">$NOTIFY_SOCKET</code> environment
                variable. If the first character of
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                <code class="varname">$NOTIFY_SOCKET</code> is "<code class="literal">@</code>", the string is
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                understood as Linux abstract namespace socket. The
                datagram is accompanied by the process credentials of
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                the sending daemon, using SCM_CREDENTIALS.</p></div><div class="refsect1"><a name="idm214198417120"></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="$NOTIFY_SOCKET"><span class="term"><code class="varname">$NOTIFY_SOCKET</code></span><a class="headerlink" title="Permalink to this term" href="#%24NOTIFY_SOCKET"></a></dt><dd><p>Set by the init system
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                                for supervised processes for status
                                and start-up completion
                                notification. This environment variable
                                specifies the socket
                                <code class="function">sd_notify()</code> talks
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                                to. See above for details.</p></dd></dl></div></div><div class="refsect1"><a name="idm214198413216"></a><h2 id="Examples">Examples<a class="headerlink" title="Permalink to this headline" href="#Examples"></a></h2><div class="example"><a name="idm214198412544"></a><p class="title"><b>Example 1. Start-up Notification</b></p><div class="example-contents"><p>When a daemon finished starting up, it
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                        might issue the following call to notify
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                        the init system:</p><pre class="programlisting">sd_notify(0, "READY=1");</pre></div></div><br class="example-break"><div class="example"><a name="idm214198410496"></a><p class="title"><b>Example 2. Extended Start-up Notification</b></p><div class="example-contents"><p>A daemon could send the following after
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                        completing initialization:</p><pre class="programlisting">sd_notifyf(0, "READY=1\n"
              "STATUS=Processing requests...\n"
              "MAINPID=%lu",
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              (unsigned long) getpid());</pre></div></div><br class="example-break"><div class="example"><a name="idm214198408368"></a><p class="title"><b>Example 3. Error Cause Notification</b></p><div class="example-contents"><p>A daemon could send the following shortly before exiting, on failure</p><pre class="programlisting">sd_notifyf(0, "STATUS=Failed to start up: %s\n"
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              "ERRNO=%i",
              strerror(errno),
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              errno);</pre></div></div><br class="example-break"></div><div class="refsect1"><a name="idm214198406240"></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>,
                        <a href="sd-daemon.html"><span class="citerefentry"><span class="refentrytitle">sd-daemon</span>(3)</span></a>,
                        <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>,
                        <a href="sd_watchdog_enabled.html"><span class="citerefentry"><span class="refentrytitle">sd_watchdog_enabled</span>(3)</span></a>
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                </p></div></div></body></html>