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-or-later -->
   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> is part of
  48     <citerefentry><refentrytitle>libsystemd</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
  49     provides APIs for new-style daemons, as implemented by the
  50     <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> service
  51     manager.</para>
  52
  53     <para>See
  54     <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  55     <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  56     <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  57     <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  58     <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  59     for more information about the functions implemented. In addition
  60     to these functions, a couple of logging prefixes are defined as
  61     macros:</para>
  62
  63     <programlisting>#define SD_EMERG   "&lt;0&gt;"  /* system is unusable */
  64 #define SD_ALERT   "&lt;1&gt;"  /* action must be taken immediately */
  65 #define SD_CRIT    "&lt;2&gt;"  /* critical conditions */
  66 #define SD_ERR     "&lt;3&gt;"  /* error conditions */
  67 #define SD_WARNING "&lt;4&gt;"  /* warning conditions */
  68 #define SD_NOTICE  "&lt;5&gt;"  /* normal but significant condition */
  69 #define SD_INFO    "&lt;6&gt;"  /* informational */
  70 #define SD_DEBUG   "&lt;7&gt;"  /* debug-level messages */</programlisting>
  71
  72     <para>These prefixes are intended to be used in conjunction with stderr-based logging (or stdout-based
  73     logging) as implemented by systemd. If a systemd service definition file is configured with
  74     <varname>StandardError=journal</varname> or <varname>StandardError=kmsg</varname> (and similar with
  75     <varname>StandardOutput=</varname>), these prefixes can be used to encode a log level in lines
  76     printed. This is similar to the kernel <function>printk()</function>-style logging. See
  77     <citerefentry><refentrytitle>klogctl</refentrytitle><manvolnum>2</manvolnum></citerefentry> for more
  78     information.</para>
  79
  80     <para>The log levels are identical to
  81     <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>'s
  82     log level system. To use these prefixes simply prefix every line
  83     with one of these strings. A line that is not prefixed will be
  84     logged at the default log level SD_INFO.</para>
  85
  86     <example>
  87       <title>Hello World</title>
  88
  89       <para>A daemon may log with the log level NOTICE by issuing this
  90       call:</para>
  91
  92       <programlisting>fprintf(stderr, SD_NOTICE "Hello World!\n");</programlisting>
  93     </example>
  94   </refsect1>
  95
  96   <xi:include href="libsystemd-pkgconfig.xml" />
  97
  98   <refsect1>
  99     <title>See Also</title>
 100     <para>
 101       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 102       <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 103       <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 104       <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 105       <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 106       <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 107       <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 108       <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 109       <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 110       <citerefentry project='man-pages'><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 111       <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 112     </para>
 113   </refsect1>
 114
 115 </refentry>