<?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 <libudev.h></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 one 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>