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1 | <?xml version='1.0'?> <!--*-nxml-*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
4 | ||
5 | <!-- | |
6 | This file is part of systemd. | |
7 | ||
8 | Copyright 2010 Lennart Poettering | |
9 | ||
10 | systemd is free software; you can redistribute it and/or modify it | |
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11 | under the terms of the GNU Lesser General Public License as published by |
12 | the Free Software Foundation; either version 2.1 of the License, or | |
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13 | (at your option) any later version. |
14 | ||
15 | systemd is distributed in the hope that it will be useful, but | |
16 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
5430f7f2 | 18 | Lesser General Public License for more details. |
f9378423 | 19 | |
5430f7f2 | 20 | You should have received a copy of the GNU Lesser General Public License |
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21 | along with systemd; If not, see <http://www.gnu.org/licenses/>. |
22 | --> | |
23 | ||
24 | <refentry id="sd-daemon"> | |
25 | ||
26 | <refentryinfo> | |
27 | <title>sd-daemon</title> | |
28 | <productname>systemd</productname> | |
29 | ||
30 | <authorgroup> | |
31 | <author> | |
32 | <contrib>Developer</contrib> | |
33 | <firstname>Lennart</firstname> | |
34 | <surname>Poettering</surname> | |
35 | <email>lennart@poettering.net</email> | |
36 | </author> | |
37 | </authorgroup> | |
38 | </refentryinfo> | |
39 | ||
40 | <refmeta> | |
41 | <refentrytitle>sd-daemon</refentrytitle> | |
42 | <manvolnum>7</manvolnum> | |
43 | </refmeta> | |
44 | ||
45 | <refnamediv> | |
46 | <refname>sd-daemon</refname> | |
47 | <refpurpose>Reference implementation of APIs for | |
48 | new-style daemons</refpurpose> | |
49 | </refnamediv> | |
50 | ||
51 | <refsynopsisdiv> | |
52 | <funcsynopsis> | |
a822cbfa | 53 | <funcsynopsisinfo>#include <systemd/sd-daemon.h></funcsynopsisinfo> |
f9378423 | 54 | </funcsynopsis> |
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55 | |
56 | <cmdsynopsis> | |
57 | <command>pkg-config --cflags --libs libsystemd-daemon</command> | |
58 | </cmdsynopsis> | |
59 | ||
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60 | </refsynopsisdiv> |
61 | ||
62 | <refsect1> | |
63 | <title>Description</title> | |
64 | ||
65 | <para><filename>sd-daemon.c</filename> and | |
66 | <filename>sd-daemon.h</filename> provide a reference | |
67 | implementation of various APIs for new-style daemons, | |
68 | as implemented by the | |
f3e219a2 | 69 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> |
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70 | init system.</para> |
71 | ||
72 | <para>See | |
73 | <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
74 | <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
75 | <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
76 | <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
77 | for more information about the functions | |
78 | implemented. In addition to these functions a couple | |
79 | of logging prefixes are defined as macros:</para> | |
80 | ||
81 | <programlisting>#define SD_EMERG "<0>" /* system is unusable */ | |
82 | #define SD_ALERT "<1>" /* action must be taken immediately */ | |
83 | #define SD_CRIT "<2>" /* critical conditions */ | |
84 | #define SD_ERR "<3>" /* error conditions */ | |
85 | #define SD_WARNING "<4>" /* warning conditions */ | |
86 | #define SD_NOTICE "<5>" /* normal but significant condition */ | |
87 | #define SD_INFO "<6>" /* informational */ | |
88 | #define SD_DEBUG "<7>" /* debug-level messages */</programlisting> | |
89 | ||
90 | <para>These prefixes are intended to be used in | |
91 | conjunction with STDERR-based logging as implemented | |
92 | by systemd. If a systemd service definition file is | |
93 | configured with <varname>StandardError=syslog</varname> | |
94 | or <varname>StandardError=kmsg</varname> these | |
95 | prefixes can be used to encode a log level in lines | |
96 | printed. This is similar to the kernel | |
97 | <function>printk()</function>-style logging. See | |
98 | <citerefentry><refentrytitle>klogctl</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
99 | for more information.</para> | |
100 | ||
101 | <para>The log levels are identical to | |
102 | <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>'s | |
103 | log level system. To use these prefixes simply prefix | |
104 | every line with one of these strings. A line that is | |
105 | not prefixed will be logged at the default log level | |
106 | SD_INFO.</para> | |
107 | ||
108 | <example> | |
109 | <title>Hello World</title> | |
110 | ||
111 | <para>A daemon may log with the log level | |
112 | NOTICE by issuing this call:</para> | |
113 | ||
114 | <programlisting>fprintf(stderr, SD_NOTICE "Hello World!\n");</programlisting> | |
115 | </example> | |
116 | </refsect1> | |
117 | ||
118 | <refsect1> | |
119 | <title>Notes</title> | |
120 | ||
121 | <para>These interfaces are provided by the reference | |
122 | implementation of APIs for new-style daemons and | |
123 | distributed with the systemd package. The algorithms | |
124 | they implement are simple, and can easily be | |
125 | reimplemented in daemons if it is important to support | |
126 | this interface without using the reference | |
127 | implementation. See the respective function man pages | |
128 | for details.</para> | |
129 | ||
130 | <para>In addition, for details about the algorithms | |
131 | check the liberally licensed reference implementation | |
132 | sources: | |
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133 | <ulink url="http://cgit.freedesktop.org/systemd/systemd/plain/src/sd-daemon.c"/> |
134 | resp. <ulink url="http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h"/></para> | |
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135 | |
136 | <para>These APIs are implemented in the reference | |
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137 | implementation's <filename>sd-daemon.c</filename> and |
138 | <filename>sd-daemon.h</filename> files. These | |
139 | interfaces are available as shared library, which can | |
140 | be compiled and linked to with the | |
141 | <literal>libsystemd-daemon</literal> | |
142 | <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
143 | file. Alternatively, applications consuming these APIs | |
144 | may copy the implementation into their source tree, | |
145 | either verbatim or in excerpts.</para> | |
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146 | |
147 | <para>The functions directly related to new-style | |
148 | daemons become NOPs when -DDISABLE_SYSTEMD is set | |
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149 | during compilation and the reference implementation is |
150 | used as drop-in files. In addition, if | |
f9378423 | 151 | <filename>sd-daemon.c</filename> is compiled on |
af62c704 | 152 | non-Linux systems they become NOPs.</para> |
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153 | </refsect1> |
154 | ||
155 | <refsect1> | |
156 | <title>See Also</title> | |
157 | <para> | |
160cd5c9 | 158 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
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159 | <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
160 | <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
161 | <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
162 | <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
163 | <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>, | |
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164 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
165 | <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
e62e6670 | 166 | <citerefentry><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
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167 | <citerefentry><refentrytitle>sd-readahead</refentrytitle><manvolnum>7</manvolnum></citerefentry>, |
168 | <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
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169 | </para> |
170 | </refsect1> | |
171 | ||
172 | </refentry> |