systemd-stable/man/libudev.xml

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<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 of 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>