<?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 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>