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build-sys: prepare release 44
[elogind.git] / man / sd_booted.xml
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
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8   Copyright 2010 Lennart Poettering
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23
24 <refentry id="sd_booted">
25
26         <refentryinfo>
27                 <title>sd_booted</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_booted</refentrytitle>
42                 <manvolnum>3</manvolnum>
43         </refmeta>
44
45         <refnamediv>
46                 <refname>sd_booted</refname>
47                 <refpurpose>Test whether the system is running the systemd init system.</refpurpose>
48         </refnamediv>
49
50         <refsynopsisdiv>
51                 <funcsynopsis>
52                         <funcsynopsisinfo>#include &lt;systemd/sd-daemon.h&gt;</funcsynopsisinfo>
53
54                         <funcprototype>
55                                 <funcdef>int <function>sd_booted</function></funcdef>
56                                 <paramdef>void</paramdef>
57                         </funcprototype>
58                 </funcsynopsis>
59         </refsynopsisdiv>
60
61         <refsect1>
62                 <title>Description</title>
63                 <para><function>sd_booted()</function> checks whether
64                 the system was booted up using the systemd init system.</para>
65         </refsect1>
66
67         <refsect1>
68                 <title>Return Value</title>
69
70                 <para>On failure, this call returns a negative
71                 errno-style error code. If the system was booted up
72                 with systemd as init system, this call returns a
73                 positive return value, zero otherwise.</para>
74         </refsect1>
75
76         <refsect1>
77                 <title>Notes</title>
78
79                 <para>This function is provided by the reference
80                 implementation of APIs for new-style daemons and
81                 distributed with the systemd package. The algorithm it
82                 implements is simple, and can easily be reimplemented
83                 in daemons if it is important to support this
84                 interface without using the reference
85                 implementation.</para>
86
87                 <para>Internally, this function checks whether the
88                 <filename>/sys/fs/cgroup/systemd</filename> virtual file
89                 system is mounted, by comparing the st_dev value of
90                 the <function>stat()</function> data of
91                 <filename>/sys/fs/cgroup</filename> and
92                 <filename>/sys/fs/cgroup/systemd</filename>.</para>
93
94                 <para>For details about the algorithm check the
95                 liberally licensed reference implementation sources:
96                 <ulink url="http://cgit.freedesktop.org/systemd/systemd/plain/src/sd-daemon.c"/>
97                 resp. <ulink
98                 url="http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h"/></para>
99
100                 <para><function>sd_booted()</function> is implemented
101                 in the reference implementation's
102                 <filename>sd-daemon.c</filename> and
103                 <filename>sd-daemon.h</filename> files. These
104                 interfaces are available as shared library, which can
105                 be compiled and linked to with the
106                 <literal>libsystemd-daemon</literal>
107                 <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
108                 file. Alternatively, applications consuming these APIs
109                 may copy the implementation into their source
110                 tree. For more details about the reference
111                 implementation see
112                 <citerefentry><refentrytitle>sd_daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
113
114                 <para>If the reference implementation is used as
115                 drop-in files and -DDISABLE_SYSTEMD is set during
116                 compilation this function will always return 0 and
117                 otherwise become a NOP.</para>
118         </refsect1>
119
120         <refsect1>
121                 <title>See Also</title>
122                 <para>
123                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
124                         <citerefentry><refentrytitle>sd_daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>
125                 </para>
126         </refsect1>
127
128 </refentry>