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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>sd_notify</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><style>
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</style><a href="index.html">Index </a>·
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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 <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_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
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>
parameter is non-zero, <code class="function">sd_notify()</code>
will unset the <code class="varname">$NOTIFY_SOCKET</code>
environment variable before returning (regardless of
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
<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">$WATCHDOG_USEC</code>
environment variable. See
<a href="sd_watchdog_enabled.html"><span class="citerefentry"><span class="refentrytitle">sd_watchdog_enabled</span>(3)</span></a>
for details.</p></dd></dl></div><p>It is recommended to prefix variable names that
are not shown in the list above with
<code class="varname">X_</code> to avoid namespace
clashes.</p><p>Note that systemd will accept status data sent
from a daemon only if the
<code class="varname">NotifyAccess=</code> option is correctly
set in the service definition file. See
<a href="systemd.service.html"><span class="citerefentry"><span class="refentrytitle">systemd.service</span>(5)</span></a>
for details.</p><p><code class="function">sd_notifyf()</code> is similar to
<code class="function">sd_notify()</code> but takes a
<code class="function">printf()</code>-like format string plus
arguments.</p></div><div class="refsect1"><a name="idm214198431088"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p>On failure, these calls return a negative
errno-style error code. If
<code class="varname">$NOTIFY_SOCKET</code> was not set and
hence no status data could be sent, 0 is returned. If
the status was sent, these functions return with a
positive return value. In order to support both, init
systems that implement this scheme and those which
do not, it is generally recommended to ignore the return
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
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
datagram with the state string as payload to the
<code class="constant">AF_UNIX</code> socket referenced in the
<code class="varname">$NOTIFY_SOCKET</code> environment
variable. If the first character of
<code class="varname">$NOTIFY_SOCKET</code> is "<code class="literal">@</code>", the string is
understood as Linux abstract namespace socket. The
datagram is accompanied by the process credentials of
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
for supervised processes for status
and start-up completion
notification. This environment variable
specifies the socket
<code class="function">sd_notify()</code> talks
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
might issue the following call to notify
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
completing initialization:</p><pre class="programlisting">sd_notifyf(0, "READY=1\n"
"STATUS=Processing requests...\n"
"MAINPID=%lu",
(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"
"ERRNO=%i",
strerror(errno),
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>
<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>,
<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>
</p></div></div></body></html>
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