man/sd_bus_track_add_name.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   Copyright 2016 Lennart Poettering
   9 -->
  10
  11 <refentry id="sd_bus_track_add_name" xmlns:xi="http://www.w3.org/2001/XInclude">
  12
  13   <refentryinfo>
  14     <title>sd_bus_track_add_name</title>
  15     <productname>systemd</productname>
  16
  17     <authorgroup>
  18       <author>
  19         <contrib>Developer</contrib>
  20         <firstname>Lennart</firstname>
  21         <surname>Poettering</surname>
  22         <email>lennart@poettering.net</email>
  23       </author>
  24     </authorgroup>
  25   </refentryinfo>
  26
  27   <refmeta>
  28     <refentrytitle>sd_bus_track_add_name</refentrytitle>
  29     <manvolnum>3</manvolnum>
  30   </refmeta>
  31
  32   <refnamediv>
  33     <refname>sd_bus_track_add_name</refname>
  34     <refname>sd_bus_track_add_sender</refname>
  35     <refname>sd_bus_track_remove_name</refname>
  36     <refname>sd_bus_track_remove_sender</refname>
  37     <refname>sd_bus_track_count</refname>
  38     <refname>sd_bus_track_count_sender</refname>
  39     <refname>sd_bus_track_count_name</refname>
  40     <refname>sd_bus_track_contains</refname>
  41     <refname>sd_bus_track_first</refname>
  42     <refname>sd_bus_track_next</refname>
  43
  44     <refpurpose>Add, remove and retrieve bus peers tracked in a bus peer tracking object</refpurpose>
  45   </refnamediv>
  46
  47   <refsynopsisdiv>
  48     <funcsynopsis>
  49       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  50
  51       <funcprototype>
  52         <funcdef>int <function>sd_bus_track_add_name</function></funcdef>
  53         <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
  54         <paramdef>const char* <parameter>name</parameter></paramdef>
  55       </funcprototype>
  56
  57       <funcprototype>
  58         <funcdef>int <function>sd_bus_track_add_sender</function></funcdef>
  59         <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
  60         <paramdef>sd_bus_message* <parameter>message</parameter></paramdef>
  61       </funcprototype>
  62
  63       <funcprototype>
  64         <funcdef>int <function>sd_bus_track_remove_name</function></funcdef>
  65         <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
  66         <paramdef>const char* <parameter>name</parameter></paramdef>
  67       </funcprototype>
  68
  69       <funcprototype>
  70         <funcdef>int <function>sd_bus_track_remove_sender</function></funcdef>
  71         <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
  72         <paramdef>sd_bus_message* <parameter>message</parameter></paramdef>
  73       </funcprototype>
  74
  75       <funcprototype>
  76         <funcdef>unsigned <function>sd_bus_track_count</function></funcdef>
  77         <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
  78       </funcprototype>
  79
  80       <funcprototype>
  81         <funcdef>int <function>sd_bus_track_count_name</function></funcdef>
  82         <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
  83         <paramdef>const char* <parameter>name</parameter></paramdef>
  84       </funcprototype>
  85
  86       <funcprototype>
  87         <funcdef>int <function>sd_bus_track_count_sender</function></funcdef>
  88         <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
  89         <paramdef>sd_bus_message* <parameter>message</parameter></paramdef>
  90       </funcprototype>
  91
  92       <funcprototype>
  93         <funcdef>int <function>sd_bus_track_contains</function></funcdef>
  94         <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
  95         <paramdef>const char* <parameter>name</parameter></paramdef>
  96       </funcprototype>
  97
  98       <funcprototype>
  99         <funcdef>const char* <function>sd_bus_track_first</function></funcdef>
 100         <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
 101       </funcprototype>
 102
 103       <funcprototype>
 104         <funcdef>const char* <function>sd_bus_track_next</function></funcdef>
 105         <paramdef>sd_bus_track* <parameter>t</parameter></paramdef>
 106       </funcprototype>
 107
 108     </funcsynopsis>
 109   </refsynopsisdiv>
 110
 111   <refsect1>
 112     <title>Description</title>
 113
 114     <para><function>sd_bus_track_add_name()</function> adds a peer to track to a bus peer tracking object. The first
 115     argument should refer to a bus peer tracking object created with
 116     <citerefentry><refentrytitle>sd_bus_track_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, the second
 117     name should refer to a D-Bus peer name to track, either in unique or well-known service format. If the name is not
 118     tracked yet it will be added to the list of names to track. If it already is being tracked and non-recursive mode
 119     is enabled, no operation is executed by this call. If recursive mode is enabled a per-name counter is increased by
 120     one each time this call is invoked, and <function>sd_bus_track_remove_name()</function> has to be called as many
 121     times as <function>sd_bus_track_add_name()</function> was invoked before in order to stop tracking of the name. Use
 122     <citerefentry><refentrytitle>sd_bus_track_set_recursive</refentrytitle><manvolnum>3</manvolnum></citerefentry> to
 123     switch from the default non-recursive mode to recursive mode, or back. Note that the specified name is tracked as
 124     it is, well-known names are not resolved to unique names by this call. Note that multiple bus peer tracking objects
 125     may track the same name.</para>
 126
 127     <para><function>sd_bus_track_remove_name()</function> undoes the effect of
 128     <function>sd_bus_track_add_name()</function> and removes a bus peer name from the list of peers to watch. Depending
 129     on whether non-recursive or recursive mode is enabled for the bus peer tracking object this call will either remove
 130     the name fully from the tracking object, or will simply decrement the per-name counter by one, removing the name
 131     only when the counter reaches zero (see above). Note that a bus peer disconnecting from the bus will implicitly
 132     remove its names fully from the bus peer tracking object, regardless of the current per-name counter.</para>
 133
 134     <para><function>sd_bus_track_add_sender()</function> and <function>sd_bus_track_remove_sender()</function> are
 135     similar to <function>sd_bus_track_add_name()</function> and <function>sd_bus_track_remove_name()</function> but
 136     take a bus message as argument. The sender of this bus message is determined and added to/removed from the bus peer
 137     tracking object. As messages always originate from unique names, and never from well-known names this means that
 138     this call will effectively only add unique names to the bus peer tracking object.</para>
 139
 140     <para><function>sd_bus_track_count()</function> returns the number of names currently being tracked by the
 141     specified bus peer tracking object. Note that this function always returns the actual number of names tracked, and
 142     hence if <function>sd_bus_track_add_name()</function> has been invoked multiple times for the same name it is only
 143     counted as one, regardless if recursive mode is used or not.</para>
 144
 145     <para><function>sd_bus_track_count_name()</function> returns the current per-name counter for the specified
 146     name. If non-recursive mode is used this returns either 1 or 0, depending on whether the specified name has been
 147     added to the tracking object before, or not. If recursive mode has been enabled, values larger than 1 may be
 148     returned too, in case <function>sd_bus_track_add_name()</function> has been called multiple times for the same
 149     name.</para>
 150
 151     <para><function>sd_bus_track_count_sender()</function> is similar to
 152     <function>sd_bus_track_count_name()</function>, but takes a bus message object and returns the per-name counter
 153     matching the sender of the message.</para>
 154
 155     <para><function>sd_bus_track_contains()</function> may be used to determine whether the specified name has been
 156     added at least once to the specified bus peer tracking object.</para>
 157
 158     <para><function>sd_bus_track_first()</function> and <function>sd_bus_track_next()</function> may be used to
 159     enumerate all names currently being tracked by the passed bus peer tracking
 160     object. <function>sd_bus_track_first()</function> returns the first entry in the object, and resets an internally
 161     maintained read index. Each subsequent invocation of <function>sd_bus_track_next()</function> returns the next name
 162     contained in the bus object. If the end is reached <constant>NULL</constant> is returned. If no names have been
 163     added to the object yet <function>sd_bus_track_first()</function> will return <constant>NULL</constant>
 164     immediately. The order in which names are returned is undefined; in particular which name is considered the first
 165     returned is not defined. If recursive mode is enabled and the same name has been added multiple times to the bus
 166     peer tracking object it is only returned once by this enumeration. If new names are added to or existing names
 167     removed from the bus peer tracking object while it is being enumerated the enumeration ends on the next invocation
 168     of <function>sd_bus_track_next()</function> as <constant>NULL</constant> is returned.</para>
 169   </refsect1>
 170
 171   <refsect1>
 172     <title>Return Value</title>
 173
 174     <para>On success, <function>sd_bus_track_add_name()</function> and <function>sd_bus_track_add_sender()</function>
 175     return 0 if the specified name has already been added to the bus peer tracking object before and positive if it
 176     hasn't. On failure, they return a negative errno-style error code.</para>
 177
 178     <para><function>sd_bus_track_remove_name()</function> and <function>sd_bus_track_remove_sender()</function> return
 179     positive if the specified name was previously tracked by the bus peer tracking object and has now been removed. In
 180     non-recursive mode, 0 is returned if the specified name was not being tracked yet. In recursive mode
 181     <constant>-EUNATCH</constant> is returned in this case. On failure, they return a negative errno-style error
 182     code.</para>
 183
 184     <para><function>sd_bus_track_count()</function> returns the number of names currently being tracked, or 0 on
 185     failure.</para>
 186
 187     <para><function>sd_bus_track_count_name()</function> and <function>sd_bus_track_count_sender()</function> return
 188     the current per-name counter for the specified name or the sender of the specified message. Zero is returned for
 189     names that are not being tracked yet, a positive value for names added at least once. Larger values than 1 are only
 190     returned in recursive mode. On failure, a negative errno-style error code is returned.</para>
 191
 192     <para><function>sd_bus_track_contains()</function> returns the passed name if it exists in the bus peer tracking
 193     object. On failure, and if the name has not been added yet <constant>NULL</constant> is returned.</para>
 194
 195     <para><function>sd_bus_track_first()</function> and <function>sd_bus_track_next()</function> return the first/next
 196     name contained in the bus peer tracking object, and <constant>NULL</constant> if the end of the enumeration is
 197     reached and on error.</para>
 198   </refsect1>
 199
 200   <refsect1>
 201     <title>Errors</title>
 202
 203     <para>Returned errors may indicate the following problems:</para>
 204
 205     <variablelist>
 206
 207       <varlistentry>
 208         <term><constant>-EUNATCH</constant></term>
 209
 210         <listitem><para><function>sd_bus_track_remove_name()</function> or
 211         <function>sd_bus_track_remove_sender()</function> have been invoked for a name not previously added to the bus
 212         peer object.</para></listitem>
 213       </varlistentry>
 214
 215       <varlistentry>
 216         <term><constant>-EINVAL</constant></term>
 217
 218         <listitem><para>Specified parameter is invalid.</para></listitem>
 219       </varlistentry>
 220
 221       <varlistentry>
 222         <term><constant>-ENOMEM</constant></term>
 223
 224         <listitem><para>Memory allocation failed.</para></listitem>
 225       </varlistentry>
 226
 227     </variablelist>
 228   </refsect1>
 229
 230   <xi:include href="libsystemd-pkgconfig.xml" />
 231
 232   <refsect1>
 233     <title>See Also</title>
 234
 235     <para>
 236       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 237       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 238       <citerefentry><refentrytitle>sd_bus_track_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 239     </para>
 240   </refsect1>
 241
 242 </refentry>