man/sd_booted.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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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 "sd-daemon.h"</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/tree/src/sd-daemon.c"/>
  97                 resp. <ulink
  98                 url="http://cgit.freedesktop.org/systemd/tree/src/sd-daemon.h"/></para>
  99
 100                 <para><function>sd_booted()</function> is implemented
 101                 in the reference implementation's drop-in
 102                 <filename>sd-daemon.c</filename> and
 103                 <filename>sd-daemon.h</filename> files. It is
 104                 recommended that applications consuming these APIs
 105                 copy the implementation into their source tree. For
 106                 more details about the reference implementation see
 107                 <citerefentry><refentrytitle>sd_daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry></para>
 108
 109                 <para>If -DDISABLE_SYSTEMD is set during compilation
 110                 this function will always return 0 and otherwise
 111                 become a NOP.</para>
 112         </refsect1>
 113
 114         <refsect1>
 115                 <title>See Also</title>
 116                 <para>
 117                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 118                         <citerefentry><refentrytitle>sd_daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 119                 </para>
 120         </refsect1>
 121
 122 </refentry>