man/libudev.xml

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   8 <!--
   9   SPDX-License-Identifier: LGPL-2.1+
  10
  11   This file is part of systemd.
  12
  13   Copyright 2015 David Herrmann <dh.herrmann@gmail.com>
  14 -->
  15
  16 <refentry id="libudev"
  17   xmlns:xi="http://www.w3.org/2001/XInclude">
  18
  19   <refentryinfo>
  20     <title>libudev</title>
  21     <productname>systemd</productname>
  22
  23     <authorgroup>
  24       <author>
  25         <contrib>Developer</contrib>
  26         <firstname>David</firstname>
  27         <surname>Herrmann</surname>
  28         <email>dh.herrmann@gmail.com</email>
  29       </author>
  30     </authorgroup>
  31   </refentryinfo>
  32
  33   <refmeta>
  34     <refentrytitle>libudev</refentrytitle>
  35     <manvolnum>3</manvolnum>
  36   </refmeta>
  37
  38   <refnamediv>
  39     <refname>libudev</refname>
  40     <refpurpose>API for enumerating and introspecting local devices</refpurpose>
  41   </refnamediv>
  42
  43   <refsynopsisdiv>
  44     <funcsynopsis>
  45       <funcsynopsisinfo>#include &lt;libudev.h&gt;</funcsynopsisinfo>
  46     </funcsynopsis>
  47
  48     <cmdsynopsis>
  49       <command>pkg-config --cflags --libs libudev</command>
  50     </cmdsynopsis>
  51   </refsynopsisdiv>
  52
  53   <refsect1>
  54     <title>Description</title>
  55
  56     <para><filename>libudev.h</filename> provides APIs to introspect
  57     and enumerate devices on the local system.</para>
  58
  59     <para>All functions require a libudev context to operate. This
  60     context can be create via
  61     <citerefentry><refentrytitle>udev_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  62     It is used to track library state and link objects together. No
  63     global state is used by libudev, everything is always linked to
  64     a udev context. Furthermore, multiple different udev contexts can
  65     be used in parallel by multiple threads. However, a single context
  66     must not be accessed by multiple threads in parallel. The caller
  67     is responsible for providing suitable locking if they intend to use
  68     it from multiple threads.</para>
  69
  70     <para>To introspect a local device on a system, a udev device
  71     object can be created via
  72     <citerefentry><refentrytitle>udev_device_new_from_syspath</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  73     and friends. The device object allows one to query current state,
  74     read and write attributes and lookup properties of the device in
  75     question.</para>
  76
  77     <para>To enumerate local devices on the system, an enumeration
  78     object can be created via
  79     <citerefentry><refentrytitle>udev_enumerate_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
  80
  81     <para>To monitor the local system for hotplugged or unplugged
  82     devices, a monitor can be created via
  83     <citerefentry><refentrytitle>udev_monitor_new_from_netlink</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
  84
  85     <para>Whenever libudev returns a list of objects, the
  86     <citerefentry><refentrytitle>udev_list_entry</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  87     API should be used to iterate, access and modify those lists.</para>
  88
  89     <para>Furthermore, libudev also exports legacy APIs that should
  90     not be used by new software (and as such are not documented as
  91     part of this manual). This includes the hardware database known
  92     as <constant>udev_hwdb</constant> (please use the new
  93     <citerefentry><refentrytitle>sd-hwdb</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  94     API instead) and the <constant>udev_queue</constant> object to
  95     query the udev daemon (which should not be used by new software
  96     at all).</para>
  97   </refsect1>
  98
  99   <refsect1>
 100     <title>See Also</title>
 101     <para>
 102       <citerefentry><refentrytitle>udev_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 103       <citerefentry><refentrytitle>udev_device_new_from_syspath</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 104       <citerefentry><refentrytitle>udev_enumerate_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 105       <citerefentry><refentrytitle>udev_monitor_new_from_netlink</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 106       <citerefentry><refentrytitle>udev_list_entry</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 107       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 108       <citerefentry><refentrytitle>sd-device</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 109       <citerefentry><refentrytitle>sd-hwdb</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 110       <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 111     </para>
 112   </refsect1>
 113
 114 </refentry>