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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 202</span><hr><div class="refentry"><a name="sd-daemon"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd-daemon, SD_EMERG, SD_ALERT, SD_CRIT, SD_ERR, SD_WARNING, SD_NOTICE, SD_INFO, SD_DEBUG — Reference implementation of APIs for

new-style daemons</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <systemd/sd-daemon.h></pre></div><div class="cmdsynopsis"><p><code class="command">pkg-config --cflags --libs libsystemd-daemon</code> </p></div></div><div class="refsect1"><a name="idp3912992"></a><h2>Description</h2><p><code class="filename">sd-daemon.c</code> and

<code class="filename">sd-daemon.h</code> provide a reference

implementation of various APIs for new-style daemons,

as implemented by the

<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>

init system.</p><p>See

<a href="sd_listen_fds.html"><span class="citerefentry"><span class="refentrytitle">sd_listen_fds</span>(3)</span></a>,

<a href="sd_notify.html"><span class="citerefentry"><span class="refentrytitle">sd_notify</span>(3)</span></a>,

<a href="sd_booted.html"><span class="citerefentry"><span class="refentrytitle">sd_booted</span>(3)</span></a>,

for more information about the functions

implemented. In addition to these functions a couple

of logging prefixes are defined as macros:</p><pre class="programlisting">#define SD_EMERG "<0>" /* system is unusable */

#define SD_ALERT "<1>" /* action must be taken immediately */

#define SD_CRIT "<2>" /* critical conditions */

#define SD_ERR "<3>" /* error conditions */

#define SD_WARNING "<4>" /* warning conditions */

#define SD_NOTICE "<5>" /* normal but significant condition */

#define SD_INFO "<6>" /* informational */

#define SD_DEBUG "<7>" /* debug-level messages */</pre><p>These prefixes are intended to be used in

conjunction with STDERR-based logging as implemented

by systemd. If a systemd service definition file is

configured with <code class="varname">StandardError=syslog</code>

or <code class="varname">StandardError=kmsg</code> these

prefixes can be used to encode a log level in lines

printed. This is similar to the kernel

<code class="function">printk()</code>-style logging. See

<a href="klogctl.html"><span class="citerefentry"><span class="refentrytitle">klogctl</span>(2)</span></a>

for more information.</p><p>The log levels are identical to

<a href="syslog.html"><span class="citerefentry"><span class="refentrytitle">syslog</span>(3)</span></a>'s

log level system. To use these prefixes simply prefix

every line with one of these strings. A line that is

not prefixed will be logged at the default log level

SD_INFO.</p><div class="example"><a name="idp25744"></a><p class="title"><b>Example 1. Hello World</b></p><div class="example-contents"><p>A daemon may log with the log level

NOTICE by issuing this call:</p><pre class="programlisting">fprintf(stderr, SD_NOTICE "Hello World!\n");</pre></div></div><br class="example-break"></div><div class="refsect1"><a name="idp27872"></a><h2>Notes</h2><p>These interfaces are provided by the reference

implementation of APIs for new-style daemons and

distributed with the systemd package. The algorithms

they implement are simple, and can easily be

reimplemented in daemons if it is important to support

this interface without using the reference

implementation. See the respective function man pages

for details.</p><p>In addition, for details about the algorithms

check the liberally licensed reference implementation

sources:

<a class="ulink" href="http://cgit.freedesktop.org/systemd/systemd/plain/src/libsystemd-daemon/sd-daemon.c" target="_top">http://cgit.freedesktop.org/systemd/systemd/plain/src/libsystemd-daemon/sd-daemon.c</a>

and <a class="ulink" href="http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h" target="_top">http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h</a></p><p>These APIs are implemented in the reference

implementation's <code class="filename">sd-daemon.c</code> and

<code class="filename">sd-daemon.h</code> files. These

interfaces are available as shared library, which can

be compiled and linked to with the

<code class="literal">libsystemd-daemon</code>

<a href="pkg-config.html"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>

file. Alternatively, applications consuming these APIs

may copy the implementation into their source tree,

either verbatim or in excerpts.</p><p>The functions directly related to new-style

daemons become NOPs when -DDISABLE_SYSTEMD is set

during compilation and the reference implementation is

used as drop-in files. In addition, if

<code class="filename">sd-daemon.c</code> is compiled on

non-Linux systems they become NOPs.</p></div><div class="refsect1"><a name="idp35984"></a><h2>See Also</h2><p>

<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,

<a href="sd_listen_fds.html"><span class="citerefentry"><span class="refentrytitle">sd_listen_fds</span>(3)</span></a>,

<a href="sd_notify.html"><span class="citerefentry"><span class="refentrytitle">sd_notify</span>(3)</span></a>,

<a href="sd_booted.html"><span class="citerefentry"><span class="refentrytitle">sd_booted</span>(3)</span></a>,

<a href="sd_is_fifo.html"><span class="citerefentry"><span class="refentrytitle">sd_is_fifo</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="systemd.socket.html"><span class="citerefentry"><span class="refentrytitle">systemd.socket</span>(5)</span></a>,

<a href="fprintf.html"><span class="citerefentry"><span class="refentrytitle">fprintf</span>(3)</span></a>,

<a href="sd-readahead.html"><span class="citerefentry"><span class="refentrytitle">sd-readahead</span>(3)</span></a>,

<a href="pkg-config.html"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>

</p></div></div></body></html>

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