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217 lines
9.3 KiB
XML
217 lines
9.3 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
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<!ENTITY % entities SYSTEM "custom-entities.ent" >
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%entities;
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]>
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<!--
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SPDX-License-Identifier: LGPL-2.1+
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This file is part of systemd.
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Copyright 2015 David Herrmann <dh.herrmann@gmail.com>
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="udev_device_new_from_syspath"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>udev_device_new_from_syspath</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>David</firstname>
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<surname>Herrmann</surname>
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<email>dh.herrmann@gmail.com</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>udev_device_new_from_syspath</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>udev_device_new_from_syspath</refname>
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<refname>udev_device_new_from_devnum</refname>
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<refname>udev_device_new_from_subsystem_sysname</refname>
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<refname>udev_device_new_from_device_id</refname>
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<refname>udev_device_new_from_environment</refname>
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<refname>udev_device_ref</refname>
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<refname>udev_device_unref</refname>
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<refpurpose>Create, acquire and release a udev device object</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <libudev.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>struct udev_device *<function>udev_device_new_from_syspath</function></funcdef>
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<paramdef>struct udev *<parameter>udev</parameter></paramdef>
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<paramdef>const char *<parameter>syspath</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>struct udev_device *<function>udev_device_new_from_devnum</function></funcdef>
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<paramdef>struct udev *<parameter>udev</parameter></paramdef>
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<paramdef>char <parameter>type</parameter></paramdef>
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<paramdef>dev_t <parameter>devnum</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>struct udev_device *<function>udev_device_new_from_subsystem_sysname</function></funcdef>
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<paramdef>struct udev *<parameter>udev</parameter></paramdef>
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<paramdef>const char *<parameter>subsystem</parameter></paramdef>
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<paramdef>const char *<parameter>sysname</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>struct udev_device *<function>udev_device_new_from_device_id</function></funcdef>
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<paramdef>struct udev *<parameter>udev</parameter></paramdef>
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<paramdef>const char *<parameter>id</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>struct udev_device *<function>udev_device_new_from_environment</function></funcdef>
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<paramdef>struct udev *<parameter>udev</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>struct udev_device *<function>udev_device_ref</function></funcdef>
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<paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>struct udev_device *<function>udev_device_unref</function></funcdef>
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<paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>udev_device_new_from_syspath</function>,
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<function>udev_device_new_from_devnum</function>,
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<function>udev_device_new_from_subsystem_sysname</function>,
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<function>udev_device_new_from_device_id</function>, and
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<function>udev_device_new_from_environment</function>
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allocate a new udev device object and returns a pointer to it. This
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object is opaque and must not be accessed by the caller via different
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means than functions provided by libudev. Initially, the reference count
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of the device is 1. You can acquire further references, and drop
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gained references via <function>udev_device_ref()</function> and
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<function>udev_device_unref()</function>. Once the reference count hits 0,
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the device object is destroyed and freed.</para>
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<para><function>udev_device_new_from_syspath</function>,
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<function>udev_device_new_from_devnum</function>,
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<function>udev_device_new_from_subsystem_sysname</function>, and
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<function>udev_device_new_from_device_id</function>
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create the device object based on information found in
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<filename>/sys</filename>, annotated with properties from the udev-internal
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device database. A syspath is any subdirectory of <filename>/sys</filename>,
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with the restriction that a subdirectory of <filename>/sys/devices</filename>
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(or a symlink to one) represents a real device and as such must contain
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a <filename>uevent</filename> file. <function>udev_device_new_from_devnum</function>
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takes a device type, which can be <constant>b</constant> for block devices or
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<constant>c</constant> for character devices, as well as a devnum (see
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<citerefentry project='man-pages'><refentrytitle>makedev</refentrytitle><manvolnum>3</manvolnum></citerefentry>).
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<function>udev_device_new_from_subsystem_sysname</function> looks up devices based
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on the provided subsystem and sysname
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(see <citerefentry><refentrytitle>udev_device_get_subsystem</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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and
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<citerefentry><refentrytitle>udev_device_get_sysname</refentrytitle><manvolnum>3</manvolnum></citerefentry>)
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and <function>udev_device_new_from_device_id</function> looks up devices based on the provided
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device ID, which is a special string in one of the following four forms:
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<table>
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<title>Device ID strings</title>
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<tgroup cols='2'>
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<colspec colname='example' />
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<colspec colname='explanation' />
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<thead><row>
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<entry>Example</entry>
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<entry>Explanation</entry>
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</row></thead>
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<tbody>
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<row><entry><varname>b8:2</varname></entry>
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<entry>block device major:minor</entry></row>
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<row><entry><varname>c128:1</varname></entry>
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<entry>char device major:minor</entry></row>
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<row><entry><varname>n3</varname></entry>
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<entry>network device ifindex</entry></row>
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<row><entry><varname>+sound:card29</varname></entry>
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<entry>kernel driver core subsystem:device name</entry></row>
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</tbody>
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</tgroup>
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</table>
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</para>
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<para><function>udev_device_new_from_environment</function>
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creates a device from the current environment (see
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<citerefentry project='man-pages'><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>).
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Each key-value pair is interpreted in the same way as if it was
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received in an uevent (see
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<citerefentry><refentrytitle>udev_monitor_receive_device</refentrytitle><manvolnum>3</manvolnum></citerefentry>).
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The keys <constant>DEVPATH</constant>, <constant>SUBSYSTEM</constant>,
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<constant>ACTION</constant>, and <constant>SEQNUM</constant> are mandatory.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>On success, <function>udev_device_new_from_syspath()</function>,
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<function>udev_device_new_from_devnum()</function>,
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<function>udev_device_new_from_subsystem_sysname()</function>,
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<function>udev_device_new_from_device_id()</function> and
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<function>udev_device_new_from_environment()</function> return a
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pointer to the allocated udev device. On failure,
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<constant>NULL</constant> is returned,
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and <varname>errno</varname> is set appropriately.
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<function>udev_device_ref()</function> returns the argument
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that it was passed, unmodified.
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<function>udev_device_unref()</function> always returns
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<constant>NULL</constant>.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>udev_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>udev_device_get_syspath</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>udev_device_has_tag</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>udev_enumerate_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>udev_monitor_new_from_netlink</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>udev_list_entry</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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</para>
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</refsect1>
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</refentry>
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