mirror of
https://github.com/systemd/systemd.git
synced 2024-12-18 14:43:33 +08:00
164 lines
7.9 KiB
XML
164 lines
7.9 KiB
XML
<?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 General Public License as published by
|
|
the Free Software Foundation; either version 2 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
|
|
General Public License for more details.
|
|
|
|
You should have received a copy of the GNU 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>7</manvolnum>
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>sd-daemon</refname>
|
|
<refpurpose>Reference implementation of APIs for
|
|
new-style daemons</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<funcsynopsis>
|
|
<funcsynopsisinfo>#include "sd-daemon.h"</funcsynopsisinfo>
|
|
</funcsynopsis>
|
|
</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 "<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 */</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/tree/src/sd-daemon.c"/>
|
|
resp. <ulink url="http://cgit.freedesktop.org/systemd/tree/src/sd-daemon.h"/></para>
|
|
|
|
<para>These APIs are implemented in the reference
|
|
implementation's drop-in
|
|
<filename>sd-daemon.c</filename> and
|
|
<filename>sd-daemon.h</filename> files. It is
|
|
recommended that applications consuming these APIs copy
|
|
the implementation into their source tree, either
|
|
verbatim or in excerpts. These interfaces are
|
|
currently not available in a dynamic library.</para>
|
|
|
|
<para>The functions directly related to new-style
|
|
daemons become NOPs when -DDISABLE_SYSTEMD is set
|
|
during compilation. 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>7</manvolnum></citerefentry>
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|