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