man/sd-daemon.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="sd-daemon"
   7   xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>sd-daemon</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>sd-daemon</refentrytitle>
  16     <manvolnum>3</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>sd-daemon</refname>
  21     <refname>SD_EMERG</refname>
  22     <refname>SD_ALERT</refname>
  23     <refname>SD_CRIT</refname>
  24     <refname>SD_ERR</refname>
  25     <refname>SD_WARNING</refname>
  26     <refname>SD_NOTICE</refname>
  27     <refname>SD_INFO</refname>
  28     <refname>SD_DEBUG</refname>
  29     <refpurpose>APIs for
  30     new-style daemons</refpurpose>
  31   </refnamediv>
  32
  33   <refsynopsisdiv>
  34     <funcsynopsis>
  35       <funcsynopsisinfo>#include &lt;systemd/sd-daemon.h&gt;</funcsynopsisinfo>
  36     </funcsynopsis>
  37
  38     <cmdsynopsis>
  39       <command>pkg-config --cflags --libs libsystemd</command>
  40     </cmdsynopsis>
  41
  42   </refsynopsisdiv>
  43
  44   <refsect1>
  45     <title>Description</title>
  46
  47     <para><filename>sd-daemon.h</filename> provides APIs for new-style
  48     daemons, as implemented by the
  49     <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  50     service manager.</para>
  51
  52     <para>See
  53     <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  54     <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  55     <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  56     <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  57     <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  58     for more information about the functions implemented. In addition
  59     to these functions, a couple of logging prefixes are defined as
  60     macros:</para>
  61
  62     <programlisting>#define SD_EMERG   "&lt;0&gt;"  /* system is unusable */
  63 #define SD_ALERT   "&lt;1&gt;"  /* action must be taken immediately */
  64 #define SD_CRIT    "&lt;2&gt;"  /* critical conditions */
  65 #define SD_ERR     "&lt;3&gt;"  /* error conditions */
  66 #define SD_WARNING "&lt;4&gt;"  /* warning conditions */
  67 #define SD_NOTICE  "&lt;5&gt;"  /* normal but significant condition */
  68 #define SD_INFO    "&lt;6&gt;"  /* informational */
  69 #define SD_DEBUG   "&lt;7&gt;"  /* debug-level messages */</programlisting>
  70
  71     <para>These prefixes are intended to be used in conjunction with
  72     stderr-based logging as implemented by systemd. If a systemd
  73     service definition file is configured with
  74     <varname>StandardError=journal</varname>,
  75     <varname>StandardError=syslog</varname> or
  76     <varname>StandardError=kmsg</varname>, these prefixes can be used
  77     to encode a log level in lines printed. This is similar to the
  78     kernel <function>printk()</function>-style logging. See
  79     <citerefentry><refentrytitle>klogctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
  80     for more information.</para>
  81
  82     <para>The log levels are identical to
  83     <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>'s
  84     log level system. To use these prefixes simply prefix every line
  85     with one of these strings. A line that is not prefixed will be
  86     logged at the default log level SD_INFO.</para>
  87
  88     <example>
  89       <title>Hello World</title>
  90
  91       <para>A daemon may log with the log level NOTICE by issuing this
  92       call:</para>
  93
  94       <programlisting>fprintf(stderr, SD_NOTICE "Hello World!\n");</programlisting>
  95     </example>
  96   </refsect1>
  97
  98   <xi:include href="libsystemd-pkgconfig.xml" />
  99
 100   <refsect1>
 101     <title>See Also</title>
 102     <para>
 103       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 104       <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 105       <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 106       <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 107       <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 108       <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 109       <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 110       <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 111       <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 112       <citerefentry project='man-pages'><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 113       <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 114     </para>
 115   </refsect1>
 116
 117 </refentry>