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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>·
<a href="systemd.directives.html">Directives </a>·
<a href="../python-systemd/index.html">Python </a>·
<a href="../libudev/index.html">libudev </a>·
<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 218</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 service 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="idm139898376842944"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description"></a></h2><p><code class="function">sd_notify()</code> may be called
by a service to notify the service manager about
state 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 service
manager that service startup is
finished. This is only used by systemd
if the service definition file has
Type=notify set. Since there is little
value in signaling non-readiness, the
only value services should send is
"<code class="literal">READY=1</code>"
(i.e. "<code class="literal">READY=0</code>" is
not defined).</p></dd><dt id="RELOADING=1"><span class="term">RELOADING=1</span><a class="headerlink" title="Permalink to this term" href="#RELOADING=1"></a></dt><dd><p>Tells the service manager
that the service is reloading its
configuration. This is useful to allow
the service manager to track the service's
internal state, and present it to the
user. Note that a service that sends
this notification must also send a
"<code class="literal">READY=1</code>"
notification when it completed
reloading its
configuration.</p></dd><dt id="STOPPING=1"><span class="term">STOPPING=1</span><a class="headerlink" title="Permalink to this term" href="#STOPPING=1"></a></dt><dd><p>Tells the service manager
that the service is beginning its
shutdown. This is useful to allow the
service manager to track the service's
internal state, and present it to the
user.</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
UTF-8 status string back to the service manager
that describes the service 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:
"<code class="literal">STATUS=Completed 66% of file
system
check...</code>"</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 service fails, the
errno-style error code, formatted as
string. Example: "<code class="literal">ERRNO=2</code>" 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 service fails, the
D-Bus error-style error code. Example:
"<code class="literal">BUSERROR=org.freedesktop.DBus.Error.TimedOut</code>"</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
service, in case the service manager did
not fork off the process
itself. Example:
"<code class="literal">MAINPID=4711</code>"</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 information how to enable this
functionality and
<a href="sd_watchdog_enabled.html"><span class="citerefentry"><span class="refentrytitle">sd_watchdog_enabled</span>(3)</span></a>
for the details of how the service can
check if the the watchdog is enabled.
</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 service 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="idm139898380706672"></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="idm139898380704544"></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="http://linux.die.net/man/1/pkg-config"><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 service, using SCM_CREDENTIALS.</p></div><div class="refsect1"><a name="idm139898380700096"></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 service manager
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="idm139898380696192"></a><h2 id="Examples">Examples<a class="headerlink" title="Permalink to this headline" href="#Examples"></a></h2><div class="example"><a name="idm139898380695520"></a><p class="title"><b>Example 1. Start-up Notification</b></p><div class="example-contents"><p>When a service finished starting up, it
might issue the following call to notify
the service manager:</p><pre class="programlisting">sd_notify(0, "READY=1");</pre></div></div><br class="example-break"><div class="example"><a name="idm139898380693472"></a><p class="title"><b>Example 2. Extended Start-up Notification</b></p><div class="example-contents"><p>A service 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="idm139898375775424"></a><p class="title"><b>Example 3. Error Cause Notification</b></p><div class="example-contents"><p>A service 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="idm139898375773376"></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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