man/sd-daemon.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
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   This file is part of systemd.
   9
  10   Copyright 2010 Lennart Poettering
  11 -->
  12
  13 <refentry id="sd-daemon"
  14   xmlns:xi="http://www.w3.org/2001/XInclude">
  15
  16   <refentryinfo>
  17     <title>sd-daemon</title>
  18     <productname>systemd</productname>
  19
  20     <authorgroup>
  21       <author>
  22         <contrib>Developer</contrib>
  23         <firstname>Lennart</firstname>
  24         <surname>Poettering</surname>
  25         <email>lennart@poettering.net</email>
  26       </author>
  27     </authorgroup>
  28   </refentryinfo>
  29
  30   <refmeta>
  31     <refentrytitle>sd-daemon</refentrytitle>
  32     <manvolnum>3</manvolnum>
  33   </refmeta>
  34
  35   <refnamediv>
  36     <refname>sd-daemon</refname>
  37     <refname>SD_EMERG</refname>
  38     <refname>SD_ALERT</refname>
  39     <refname>SD_CRIT</refname>
  40     <refname>SD_ERR</refname>
  41     <refname>SD_WARNING</refname>
  42     <refname>SD_NOTICE</refname>
  43     <refname>SD_INFO</refname>
  44     <refname>SD_DEBUG</refname>
  45     <refpurpose>APIs for
  46     new-style daemons</refpurpose>
  47   </refnamediv>
  48
  49   <refsynopsisdiv>
  50     <funcsynopsis>
  51       <funcsynopsisinfo>#include &lt;systemd/sd-daemon.h&gt;</funcsynopsisinfo>
  52     </funcsynopsis>
  53
  54     <cmdsynopsis>
  55       <command>pkg-config --cflags --libs libsystemd</command>
  56     </cmdsynopsis>
  57
  58   </refsynopsisdiv>
  59
  60   <refsect1>
  61     <title>Description</title>
  62
  63     <para><filename>sd-daemon.h</filename> provides APIs for new-style
  64     daemons, as implemented by the
  65     <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  66     service manager.</para>
  67
  68     <para>See
  69     <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  70     <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  71     <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  72     <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  73     <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  74     for more information about the functions implemented. In addition
  75     to these functions, a couple of logging prefixes are defined as
  76     macros:</para>
  77
  78     <programlisting>#define SD_EMERG   "&lt;0&gt;"  /* system is unusable */
  79 #define SD_ALERT   "&lt;1&gt;"  /* action must be taken immediately */
  80 #define SD_CRIT    "&lt;2&gt;"  /* critical conditions */
  81 #define SD_ERR     "&lt;3&gt;"  /* error conditions */
  82 #define SD_WARNING "&lt;4&gt;"  /* warning conditions */
  83 #define SD_NOTICE  "&lt;5&gt;"  /* normal but significant condition */
  84 #define SD_INFO    "&lt;6&gt;"  /* informational */
  85 #define SD_DEBUG   "&lt;7&gt;"  /* debug-level messages */</programlisting>
  86
  87     <para>These prefixes are intended to be used in conjunction with
  88     stderr-based logging as implemented by systemd. If a systemd
  89     service definition file is configured with
  90     <varname>StandardError=journal</varname>,
  91     <varname>StandardError=syslog</varname> or
  92     <varname>StandardError=kmsg</varname>, these prefixes can be used
  93     to encode a log level in lines printed. This is similar to the
  94     kernel <function>printk()</function>-style logging. See
  95     <citerefentry><refentrytitle>klogctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
  96     for more information.</para>
  97
  98     <para>The log levels are identical to
  99     <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>'s
 100     log level system. To use these prefixes simply prefix every line
 101     with one of these strings. A line that is not prefixed will be
 102     logged at the default log level SD_INFO.</para>
 103
 104     <example>
 105       <title>Hello World</title>
 106
 107       <para>A daemon may log with the log level NOTICE by issuing this
 108       call:</para>
 109
 110       <programlisting>fprintf(stderr, SD_NOTICE "Hello World!\n");</programlisting>
 111     </example>
 112   </refsect1>
 113
 114   <xi:include href="libsystemd-pkgconfig.xml" />
 115
 116   <refsect1>
 117     <title>See Also</title>
 118     <para>
 119       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 120       <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 121       <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 122       <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 123       <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 124       <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 125       <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 126       <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 127       <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 128       <citerefentry project='man-pages'><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 129       <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 130     </para>
 131   </refsect1>
 132
 133 </refentry>