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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
<!ENTITY % entities SYSTEM "custom-entities.ent" >
%entities;
]>

<!--
  This file is part of systemd.

  Copyright 2015 David Herrmann <dh.herrmann@gmail.com>

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->

<refentry id="libudev"
  xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>libudev</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>Developer</contrib>
        <firstname>David</firstname>
        <surname>Herrmann</surname>
        <email>dh.herrmann@gmail.com</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>libudev</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>libudev</refname>
    <refpurpose>API for enumerating and introspecting local devices</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;libudev.h&gt;</funcsynopsisinfo>
    </funcsynopsis>

    <cmdsynopsis>
      <command>pkg-config --cflags --libs libudev</command>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><filename>libudev.h</filename> provides APIs to introspect
    and enumerate devices on the local system.</para>

    <para>All functions require a libudev context to operate. This
    context can be create via
    <citerefentry><refentrytitle>udev_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
    It is used to track library state and link objects together. No
    global state is used by libudev, everything is always linked to
    a udev context. Furthermore, multiple different udev contexts can
    be used in parallel by multiple threads. However, a single context
    must not be accessed by multiple threads in parallel. The caller
    is responsible for providing suitable locking if they intend to use
    it from multiple threads.</para>

    <para>To introspect a local device on a system, a udev device
    object can be created via
    <citerefentry><refentrytitle>udev_device_new_from_syspath</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    and friends. The device object allows to query current state,
    read and write attributes and lookup properties of the device in
    question.</para>

    <para>To enumerate local devices on the system, an enumeration
    object can be created via
    <citerefentry><refentrytitle>udev_enumerate_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>

    <para>To monitor the local system for hotplugged or unplugged
    devices, a monitor can be created via
    <citerefentry><refentrytitle>udev_monitor_new_from_netlink</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>

    <para>Whenever libudev returns a list of objects, the
    <citerefentry><refentrytitle>udev_list_entry</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    API should be used to iterate, access and modify those lists.</para>

    <para>Furthermore, libudev also exports legacy APIs that should
    not be used by new software (and as such are not documented as
    part of this manual). This includes the hardware database known
    as <constant>udev_hwdb</constant> (please use the new
    <citerefentry><refentrytitle>sd-hwdb</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    API instead) and the <constant>udev_queue</constant> object to
    query the udev daemon (which should not be used by new software
    at all).</para>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <citerefentry><refentrytitle>udev_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>udev_device_new_from_syspath</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>udev_enumerate_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>udev_monitor_new_from_netlink</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>udev_list_entry</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd-device</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd-hwdb</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>