man/udev_device_has_tag.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
   4 <!ENTITY % entities SYSTEM "custom-entities.ent" >
   5 %entities;
   6 ]>
   7 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   8
   9 <refentry id="udev_device_has_tag"
  10   xmlns:xi="http://www.w3.org/2001/XInclude">
  11
  12   <refentryinfo>
  13     <title>udev_device_has_tag</title>
  14     <productname>systemd</productname>
  15   </refentryinfo>
  16
  17   <refmeta>
  18     <refentrytitle>udev_device_has_tag</refentrytitle>
  19     <manvolnum>3</manvolnum>
  20   </refmeta>
  21
  22   <refnamediv>
  23     <refname>udev_device_has_tag</refname>
  24     <refname>udev_device_has_current_tag</refname>
  25     <refname>udev_device_get_devlinks_list_entry</refname>
  26     <refname>udev_device_get_properties_list_entry</refname>
  27     <refname>udev_device_get_tags_list_entry</refname>
  28     <refname>udev_device_get_current_tags_list_entry</refname>
  29     <refname>udev_device_get_sysattr_list_entry</refname>
  30     <refname>udev_device_get_property_value</refname>
  31     <refname>udev_device_get_sysattr_value</refname>
  32     <refname>udev_device_set_sysattr_value</refname>
  33
  34     <refpurpose>Retrieve or set device attributes</refpurpose>
  35   </refnamediv>
  36
  37   <refsynopsisdiv>
  38     <funcsynopsis>
  39       <funcsynopsisinfo>#include &lt;libudev.h&gt;</funcsynopsisinfo>
  40
  41       <funcprototype>
  42         <funcdef>int <function>udev_device_has_tag</function></funcdef>
  43         <paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
  44         <paramdef>const char *<parameter>tag</parameter></paramdef>
  45       </funcprototype>
  46
  47       <funcprototype>
  48         <funcdef>int <function>udev_device_has_current_tag</function></funcdef>
  49         <paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
  50         <paramdef>const char *<parameter>tag</parameter></paramdef>
  51       </funcprototype>
  52
  53       <funcprototype>
  54         <funcdef>struct udev_list_entry *<function>udev_device_get_devlinks_list_entry</function></funcdef>
  55         <paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
  56       </funcprototype>
  57
  58       <funcprototype>
  59         <funcdef>struct udev_list_entry *<function>udev_device_get_properties_list_entry</function></funcdef>
  60         <paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
  61       </funcprototype>
  62
  63       <funcprototype>
  64         <funcdef>struct udev_list_entry *<function>udev_device_get_tags_list_entry</function></funcdef>
  65         <paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
  66       </funcprototype>
  67
  68       <funcprototype>
  69         <funcdef>struct udev_list_entry *<function>udev_device_get_current_tags_list_entry</function></funcdef>
  70         <paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
  71       </funcprototype>
  72
  73       <funcprototype>
  74         <funcdef>struct udev_list_entry *<function>udev_device_get_sysattr_list_entry</function></funcdef>
  75         <paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
  76       </funcprototype>
  77
  78       <funcprototype>
  79         <funcdef>const char *<function>udev_device_get_property_value</function></funcdef>
  80         <paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
  81         <paramdef>const char *<parameter>key</parameter></paramdef>
  82       </funcprototype>
  83
  84       <funcprototype>
  85         <funcdef>const char *<function>udev_device_get_sysattr_value</function></funcdef>
  86         <paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
  87         <paramdef>const char *<parameter>sysattr</parameter></paramdef>
  88       </funcprototype>
  89
  90       <funcprototype>
  91         <funcdef>int <function>udev_device_set_sysattr_value</function></funcdef>
  92         <paramdef>struct udev_device *<parameter>udev_device</parameter></paramdef>
  93         <paramdef>const char *<parameter>sysattr</parameter></paramdef>
  94         <paramdef>const char *<parameter>value</parameter></paramdef>
  95       </funcprototype>
  96
  97     </funcsynopsis>
  98   </refsynopsisdiv>
  99
 100   <refsect1>
 101     <title>Description</title>
 102
 103     <para><function>udev_device_has_tag()</function> returns a valuer larger than zero if the specified
 104     device object has the indicated tag assigned to it, and zero otherwise. See
 105     <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry> for details on
 106     the tags concept. <function>udev_device_has_current_tag()</function> executes a similar check, however
 107     only determines whether the indicated tag was set as result of the most recent event seen for the
 108     device. Tags are "sticky", i.e. once set for a device they remain on the device until the device is
 109     unplugged, even if the rules run for later events of the same device do not set them anymore. Any tag for
 110     which <function>udev_device_has_current_tag()</function> returns true will hence also return true when
 111     passed to <function>udev_device_has_tag()</function>, but the opposite might not be true, in case a tag is
 112     no longer configured by the rules applied to the most recent device even.</para>
 113
 114     <para><function>udev_device_get_tags_list_entry()</function> returns a a
 115     <function>udev_list_entry</function> object, encapsulating a list of tags set for the specified
 116     device. Similar, <function>udev_device_get_current_tags_list_entry()</function> returns a list of tags
 117     set for the specified device as effect of the most recent device event seen (see above for details on the
 118     difference).</para>
 119   </refsect1>
 120
 121   <refsect1>
 122     <title>Return Value</title>
 123
 124     <para>On success, <function>udev_device_has_tag()</function> and
 125     <function>udev_device_has_current_tag()</function> return positive or <constant>0</constant>, depending
 126     on whether the device has the given tag or not.  On failure, a negative error code is returned.</para>
 127
 128     <para>On success, <function>udev_device_get_devlinks_list_entry()</function>,
 129     <function>udev_device_get_properties_list_entry()</function>,
 130     <function>udev_device_get_tags_list_entry()</function>,
 131     <function>udev_device_get_current_tags_list_entry()</function> and
 132     <function>udev_device_get_sysattr_list_entry()</function> return a pointer to the first entry of the
 133     retrieved list. If that list is empty, or if an error occurred, <constant>NULL</constant> is
 134     returned.</para>
 135
 136     <para>On success,
 137     <function>udev_device_get_property_value()</function> and
 138     <function>udev_device_get_sysattr_value()</function> return a
 139     pointer to a constant string of the requested value. On error,
 140     <constant>NULL</constant> is returned. Attributes that may
 141     contain <constant>NUL</constant> bytes should not be retrieved
 142     with <function>udev_device_get_sysattr_value()</function>;
 143     instead, read them directly from the files within the device's
 144     <property>syspath</property>.</para>
 145
 146     <para>On success,
 147     <function>udev_device_set_sysattr_value()</function> returns
 148     an integer greater than, or equal to, <constant>0</constant>.
 149     On failure, a negative error code is returned. Values that
 150     contain <constant>NUL</constant> bytes should not be set with
 151     this function; instead, write them directly to the files within
 152     the device's <property>syspath</property>.</para>
 153   </refsect1>
 154
 155   <refsect1>
 156     <title>See Also</title>
 157
 158     <para>
 159       <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 160       <citerefentry><refentrytitle>udev_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 161       <citerefentry><refentrytitle>udev_device_new_from_syspath</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 162       <citerefentry><refentrytitle>udev_device_get_syspath</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 163       <citerefentry><refentrytitle>udev_enumerate_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 164       <citerefentry><refentrytitle>udev_monitor_new_from_netlink</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 165       <citerefentry><refentrytitle>udev_list_entry</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 166       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 167     </para>
 168   </refsect1>
 169
 170 </refentry>