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+<?xml version='1.0'?> <!--*-nxml-*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!--
+ This file is part of systemd.
+
+ Copyright 2010 Lennart Poettering
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<refentry id="sd-daemon">
+
+ <refentryinfo>
+ <title>sd-daemon</title>
+ <productname>systemd</productname>
+
+ <authorgroup>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Lennart</firstname>
+ <surname>Poettering</surname>
+ <email>lennart@poettering.net</email>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>sd-daemon</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd-daemon</refname>
+ <refname>SD_EMERG</refname>
+ <refname>SD_ALERT</refname>
+ <refname>SD_CRIT</refname>
+ <refname>SD_ERR</refname>
+ <refname>SD_WARNING</refname>
+ <refname>SD_NOTICE</refname>
+ <refname>SD_INFO</refname>
+ <refname>SD_DEBUG</refname>
+ <refpurpose>Reference implementation of APIs for
+ new-style daemons</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include &lt;systemd/sd-daemon.h&gt;</funcsynopsisinfo>
+ </funcsynopsis>
+
+ <cmdsynopsis>
+ <command>pkg-config --cflags --libs libsystemd-daemon</command>
+ </cmdsynopsis>
+
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><filename>sd-daemon.c</filename> and
+ <filename>sd-daemon.h</filename> provide a reference
+ implementation of various APIs for new-style daemons,
+ as implemented by the
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ init system.</para>
+
+ <para>See
+ <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ for more information about the functions
+ implemented. In addition to these functions a couple
+ of logging prefixes are defined as macros:</para>
+
+ <programlisting>#define SD_EMERG "&lt;0&gt;" /* system is unusable */
+#define SD_ALERT "&lt;1&gt;" /* action must be taken immediately */
+#define SD_CRIT "&lt;2&gt;" /* critical conditions */
+#define SD_ERR "&lt;3&gt;" /* error conditions */
+#define SD_WARNING "&lt;4&gt;" /* warning conditions */
+#define SD_NOTICE "&lt;5&gt;" /* normal but significant condition */
+#define SD_INFO "&lt;6&gt;" /* informational */
+#define SD_DEBUG "&lt;7&gt;" /* debug-level messages */</programlisting>
+
+ <para>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 <varname>StandardError=syslog</varname>
+ or <varname>StandardError=kmsg</varname> these
+ prefixes can be used to encode a log level in lines
+ printed. This is similar to the kernel
+ <function>printk()</function>-style logging. See
+ <citerefentry><refentrytitle>klogctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ for more information.</para>
+
+ <para>The log levels are identical to
+ <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>'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.</para>
+
+ <example>
+ <title>Hello World</title>
+
+ <para>A daemon may log with the log level
+ NOTICE by issuing this call:</para>
+
+ <programlisting>fprintf(stderr, SD_NOTICE "Hello World!\n");</programlisting>
+ </example>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <para>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.</para>
+
+ <para>In addition, for details about the algorithms
+ check the liberally licensed reference implementation
+ sources:
+ <ulink url="http://cgit.freedesktop.org/systemd/systemd/plain/src/libsystemd-daemon/sd-daemon.c"/>
+ and <ulink url="http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h"/></para>
+
+ <para>These APIs are implemented in the reference
+ implementation's <filename>sd-daemon.c</filename> and
+ <filename>sd-daemon.h</filename> files. These
+ interfaces are available as shared library, which can
+ be compiled and linked to with the
+ <literal>libsystemd-daemon</literal>
+ <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ file. Alternatively, applications consuming these APIs
+ may copy the implementation into their source tree,
+ either verbatim or in excerpts.</para>
+
+ <para>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
+ <filename>sd-daemon.c</filename> is compiled on
+ non-Linux systems they become NOPs.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd-readahead</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>