171 lines
8.1 KiB
XML
171 lines
8.1 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//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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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="udev_device_has_tag"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>udev_device_has_tag</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>udev_device_has_tag</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_has_tag</refname>
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<refname>udev_device_has_current_tag</refname>
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<refname>udev_device_get_devlinks_list_entry</refname>
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<refname>udev_device_get_properties_list_entry</refname>
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<refname>udev_device_get_tags_list_entry</refname>
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<refname>udev_device_get_current_tags_list_entry</refname>
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<refname>udev_device_get_sysattr_list_entry</refname>
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<refname>udev_device_get_property_value</refname>
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<refname>udev_device_get_sysattr_value</refname>
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<refname>udev_device_set_sysattr_value</refname>
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<refpurpose>Retrieve or set device attributes</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>int <function>udev_device_has_tag</function></funcdef>
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<paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
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<paramdef>const char *<parameter>tag</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>udev_device_has_current_tag</function></funcdef>
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<paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
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<paramdef>const char *<parameter>tag</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>struct udev_list_entry *<function>udev_device_get_devlinks_list_entry</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_list_entry *<function>udev_device_get_properties_list_entry</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_list_entry *<function>udev_device_get_tags_list_entry</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_list_entry *<function>udev_device_get_current_tags_list_entry</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_list_entry *<function>udev_device_get_sysattr_list_entry</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>const char *<function>udev_device_get_property_value</function></funcdef>
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<paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
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<paramdef>const char *<parameter>key</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>const char *<function>udev_device_get_sysattr_value</function></funcdef>
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<paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
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<paramdef>const char *<parameter>sysattr</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>udev_device_set_sysattr_value</function></funcdef>
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<paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
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<paramdef>const char *<parameter>sysattr</parameter></paramdef>
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<paramdef>const char *<parameter>value</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_has_tag()</function> returns a valuer larger than zero if the specified
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device object has the indicated tag assigned to it, and zero otherwise. See
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<citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry> for details on
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the tags concept. <function>udev_device_has_current_tag()</function> executes a similar check, however
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only determines whether the indicated tag was set as result of the most recent event seen for the
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device. Tags are "sticky", i.e. once set for a device they remain on the device until the device is
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unplugged, even if the rules run for later events of the same device do not set them anymore. Any tag for
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which <function>udev_device_has_current_tag()</function> returns true will hence also return true when
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passed to <function>udev_device_has_tag()</function>, but the opposite might not be true, in case a tag is
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no longer configured by the rules applied to the most recent device even.</para>
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<para><function>udev_device_get_tags_list_entry()</function> returns a
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<structname>udev_list_entry</structname> object, encapsulating a list of tags set for the specified
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device. Similar, <function>udev_device_get_current_tags_list_entry()</function> returns a list of tags
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set for the specified device as effect of the most recent device event seen (see above for details on the
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difference).</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_has_tag()</function> and
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<function>udev_device_has_current_tag()</function> return positive or <constant>0</constant>, depending
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on whether the device has the given tag or not. On failure, a negative error code is returned.</para>
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<para>On success, <function>udev_device_get_devlinks_list_entry()</function>,
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<function>udev_device_get_properties_list_entry()</function>,
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<function>udev_device_get_tags_list_entry()</function>,
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<function>udev_device_get_current_tags_list_entry()</function> and
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<function>udev_device_get_sysattr_list_entry()</function> return a pointer to the first entry of the
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retrieved list. If that list is empty, or if an error occurred, <constant>NULL</constant> is
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returned.</para>
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<para>On success,
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<function>udev_device_get_property_value()</function> and
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<function>udev_device_get_sysattr_value()</function> return a
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pointer to a constant string of the requested value. On error,
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<constant>NULL</constant> is returned. Attributes that may
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contain <constant>NUL</constant> bytes should not be retrieved
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with <function>udev_device_get_sysattr_value()</function>;
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instead, read them directly from the files within the device's
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<property>syspath</property>.</para>
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<para>On success,
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<function>udev_device_set_sysattr_value()</function> returns
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an integer greater than, or equal to, <constant>0</constant>.
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On failure, a negative error code is returned. Values that
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contain <constant>NUL</constant> bytes should not be set with
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this function; instead, write them directly to the files within
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the device's <property>syspath</property>.</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</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>udev_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>udev_device_new_from_syspath</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_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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