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1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> |
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 | <!-- | |
572eb058 ZJS |
6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
ecddb2b5 LP |
8 | This file is part of systemd. |
9 | ||
10 | Copyright 2016 Lennart Poettering | |
11 | ||
12 | systemd is free software; you can redistribute it and/or modify it | |
13 | under the terms of the GNU Lesser General Public License as published by | |
14 | the Free Software Foundation; either version 2.1 of the License, or | |
15 | (at your option) any later version. | |
16 | ||
17 | systemd is distributed in the hope that it will be useful, but | |
18 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
20 | Lesser General Public License for more details. | |
21 | ||
22 | You should have received a copy of the GNU Lesser General Public License | |
23 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
24 | --> | |
25 | ||
26 | <refentry id="sd_bus_track_add_name"> | |
27 | ||
28 | <refentryinfo> | |
29 | <title>sd_bus_track_add_name</title> | |
30 | <productname>systemd</productname> | |
31 | ||
32 | <authorgroup> | |
33 | <author> | |
34 | <contrib>Developer</contrib> | |
35 | <firstname>Lennart</firstname> | |
36 | <surname>Poettering</surname> | |
37 | <email>lennart@poettering.net</email> | |
38 | </author> | |
39 | </authorgroup> | |
40 | </refentryinfo> | |
41 | ||
42 | <refmeta> | |
43 | <refentrytitle>sd_bus_track_add_name</refentrytitle> | |
44 | <manvolnum>3</manvolnum> | |
45 | </refmeta> | |
46 | ||
47 | <refnamediv> | |
48 | <refname>sd_bus_track_add_name</refname> | |
49 | <refname>sd_bus_track_add_sender</refname> | |
50 | <refname>sd_bus_track_remove_name</refname> | |
51 | <refname>sd_bus_track_remove_sender</refname> | |
52 | <refname>sd_bus_track_count</refname> | |
53 | <refname>sd_bus_track_count_sender</refname> | |
54 | <refname>sd_bus_track_count_name</refname> | |
55 | <refname>sd_bus_track_contains</refname> | |
56 | <refname>sd_bus_track_first</refname> | |
57 | <refname>sd_bus_track_next</refname> | |
58 | ||
59 | <refpurpose>Add, remove and retrieve bus peers tracked in a bus peer tracking object</refpurpose> | |
60 | </refnamediv> | |
61 | ||
62 | <refsynopsisdiv> | |
63 | <funcsynopsis> | |
64 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
65 | ||
66 | <funcprototype> | |
67 | <funcdef>int <function>sd_bus_track_add_name</function></funcdef> | |
68 | <paramdef>sd_bus_track* <parameter>t</parameter></paramdef> | |
69 | <paramdef>const char* <parameter>name</parameter></paramdef> | |
70 | </funcprototype> | |
71 | ||
72 | <funcprototype> | |
73 | <funcdef>int <function>sd_bus_track_add_sender</function></funcdef> | |
74 | <paramdef>sd_bus_track* <parameter>t</parameter></paramdef> | |
75 | <paramdef>sd_bus_message* <parameter>message</parameter></paramdef> | |
76 | </funcprototype> | |
77 | ||
78 | <funcprototype> | |
79 | <funcdef>int <function>sd_bus_track_remove_name</function></funcdef> | |
80 | <paramdef>sd_bus_track* <parameter>t</parameter></paramdef> | |
81 | <paramdef>const char* <parameter>name</parameter></paramdef> | |
82 | </funcprototype> | |
83 | ||
84 | <funcprototype> | |
85 | <funcdef>int <function>sd_bus_track_remove_sender</function></funcdef> | |
86 | <paramdef>sd_bus_track* <parameter>t</parameter></paramdef> | |
87 | <paramdef>sd_bus_message* <parameter>message</parameter></paramdef> | |
88 | </funcprototype> | |
89 | ||
90 | <funcprototype> | |
91 | <funcdef>unsigned <function>sd_bus_track_count</function></funcdef> | |
92 | <paramdef>sd_bus_track* <parameter>t</parameter></paramdef> | |
93 | </funcprototype> | |
94 | ||
95 | <funcprototype> | |
96 | <funcdef>int <function>sd_bus_track_count_name</function></funcdef> | |
97 | <paramdef>sd_bus_track* <parameter>t</parameter></paramdef> | |
98 | <paramdef>const char* <parameter>name</parameter></paramdef> | |
99 | </funcprototype> | |
100 | ||
101 | <funcprototype> | |
102 | <funcdef>int <function>sd_bus_track_count_sender</function></funcdef> | |
103 | <paramdef>sd_bus_track* <parameter>t</parameter></paramdef> | |
104 | <paramdef>sd_bus_message* <parameter>message</parameter></paramdef> | |
105 | </funcprototype> | |
106 | ||
107 | <funcprototype> | |
108 | <funcdef>int <function>sd_bus_track_contains</function></funcdef> | |
109 | <paramdef>sd_bus_track* <parameter>t</parameter></paramdef> | |
110 | <paramdef>const char* <parameter>name</parameter></paramdef> | |
111 | </funcprototype> | |
112 | ||
113 | <funcprototype> | |
114 | <funcdef>const char* <function>sd_bus_track_first</function></funcdef> | |
115 | <paramdef>sd_bus_track* <parameter>t</parameter></paramdef> | |
116 | </funcprototype> | |
117 | ||
118 | <funcprototype> | |
119 | <funcdef>const char* <function>sd_bus_track_next</function></funcdef> | |
120 | <paramdef>sd_bus_track* <parameter>t</parameter></paramdef> | |
121 | </funcprototype> | |
122 | ||
123 | </funcsynopsis> | |
124 | </refsynopsisdiv> | |
125 | ||
126 | <refsect1> | |
127 | <title>Description</title> | |
128 | ||
129 | <para><function>sd_bus_track_add_name()</function> adds a peer to track to a bus peer tracking object. The first | |
130 | argument should refer to a bus peer tracking object created with | |
131 | <citerefentry><refentrytitle>sd_bus_track_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, the second | |
132 | name should refer to a D-Bus peer name to track, either in unique or well-known service format. If the name is not | |
133 | tracked yet it will be added to the list of names to track. If it already is being tracked and non-recursive mode | |
134 | is enabled, no operation is executed by this call. If recursive mode is enabled a per-name counter is increased by | |
135 | one each time this call is invoked, and <function>sd_bus_track_remove_name()</function> has to be called as many | |
136 | times as <function>sd_bus_track_add_name()</function> was invoked before in order to stop tracking of the name. Use | |
137 | <citerefentry><refentrytitle>sd_bus_track_set_recursive</refentrytitle><manvolnum>3</manvolnum></citerefentry> to | |
138 | switch from the default non-recursive mode to recursive mode, or back. Note that the specified name is tracked as | |
139 | it is, well-known names are not resolved to unique names by this call. Note that multiple bus peer tracking objects | |
140 | may track the same name.</para> | |
141 | ||
142 | <para><function>sd_bus_track_remove_name()</function> undoes the effect of | |
143 | <function>sd_bus_track_add_name()</function> and removes a bus peer name from the list of peers to watch. Depending | |
144 | on whether non-recursive or recursive mode is enabled for the bus peer tracking object this call will either remove | |
145 | the name fully from the tracking object, or will simply decrement the per-name counter by one, removing the name | |
146 | only when the counter reaches zero (see above). Note that a bus peer disconnecting from the bus will implicitly | |
147 | remove its names fully from the bus peer tracking object, regardless of the current per-name counter.</para> | |
148 | ||
149 | <para><function>sd_bus_track_add_sender()</function> and <function>sd_bus_track_remove_sender()</function> are | |
150 | similar to <function>sd_bus_track_add_name()</function> and <function>sd_bus_track_remove_name()</function> but | |
151 | take a bus message as argument. The sender of this bus message is determined and added to/removed from the bus peer | |
152 | tracking object. As messages always originate from unique names, and never from well-known names this means that | |
153 | this call will effectively only add unique names to the bus peer tracking object.</para> | |
154 | ||
155 | <para><function>sd_bus_track_count()</function> returns the number of names currently being tracked by the | |
156 | specified bus peer tracking object. Note that this function always returns the actual number of names tracked, and | |
157 | hence if <function>sd_bus_track_add_name()</function> has been invoked multiple times for the same name it is only | |
158 | counted as one, regardless if recursive mode is used or not.</para> | |
159 | ||
160 | <para><function>sd_bus_track_count_name()</function> returns the current per-name counter for the specified | |
161 | name. If non-recursive mode is used this returns either 1 or 0, depending on whether the specified name has been | |
162 | added to the tracking object before, or not. If recursive mode has been enabled, values larger than 1 may be | |
163 | returned too, in case <function>sd_bus_track_add_name()</function> has been called multiple times for the same | |
164 | name.</para> | |
165 | ||
166 | <para><function>sd_bus_track_count_sender()</function> is similar to | |
167 | <function>sd_bus_track_count_name()</function>, but takes a bus message object and returns the per-name counter | |
168 | matching the sender of the message.</para> | |
169 | ||
170 | <para><function>sd_bus_track_contains()</function> may be used to determine whether the specified name has been | |
171 | added at least once to the specified bus peer tracking object.</para> | |
172 | ||
173 | <para><function>sd_bus_track_first()</function> and <function>sd_bus_track_next()</function> may be used to | |
174 | enumerate all names currently being tracked by the passed bus peer tracking | |
175 | object. <function>sd_bus_track_first()</function> returns the first entry in the object, and resets an internally | |
176 | maintained read index. Each subsequent invocation of <function>sd_bus_track_next()</function> returns the next name | |
177 | contained in the bus object. If the end is reached <constant>NULL</constant> is returned. If no names have been | |
178 | added to the object yet <function>sd_bus_track_first()</function> will return <constant>NULL</constant> | |
179 | immediately. The order in which names are returned is undefined; in particular which name is considered the first | |
180 | returned is not defined. If recursive mode is enabled and the same name has been added multiple times to the bus | |
181 | peer tracking object it is only returned once by this enumeration. If new names are added to or existing names | |
182 | removed from the bus peer tracking object while it is being enumerated the enumeration ends on the next invocation | |
183 | of <function>sd_bus_track_next()</function> as <constant>NULL</constant> is returned.</para> | |
184 | </refsect1> | |
185 | ||
186 | <refsect1> | |
187 | <title>Return Value</title> | |
188 | ||
189 | <para>On success, <function>sd_bus_track_add_name()</function> and <function>sd_bus_track_add_sender()</function> | |
190 | return 0 if the specified name has already been added to the bus peer tracking object before and positive if it | |
191 | hasn't. On failure, they return a negative errno-style error code.</para> | |
192 | ||
193 | <para><function>sd_bus_track_remove_name()</function> and <function>sd_bus_track_remove_sender()</function> return | |
194 | positive if the specified name was previously tracked by the bus peer tracking object and has now been removed. In | |
195 | non-recursive mode, 0 is returned if the specified name was not being tracked yet. In recursive mode | |
196 | <constant>-EUNATCH</constant> is returned in this case. On failure, they return a negative errno-style error | |
197 | code.</para> | |
198 | ||
199 | <para><function>sd_bus_track_count()</function> returns the number of names currently being tracked, or 0 on | |
200 | failure.</para> | |
201 | ||
202 | <para><function>sd_bus_track_count_name()</function> and <function>sd_bus_track_count_sender()</function> return | |
203 | the current per-name counter for the specified name or the sender of the specified message. Zero is returned for | |
204 | names that are not being tracked yet, a positive value for names added at least once. Larger values than 1 are only | |
205 | returned in recursive mode. On failure, a negative errno-style error code is returned.</para> | |
206 | ||
207 | <para><function>sd_bus_track_contains()</function> returns the passed name if it exists in the bus peer tracking | |
208 | object. On failure, and if the name has not been added yet <constant>NULL</constant> is returned.</para> | |
209 | ||
210 | <para><function>sd_bus_track_first()</function> and <function>sd_bus_track_next()</function> return the first/next | |
211 | name contained in the bus peer tracking object, and <constant>NULL</constant> if the end of the enumeration is | |
212 | reached and on error.</para> | |
213 | </refsect1> | |
214 | ||
215 | <refsect1> | |
216 | <title>Errors</title> | |
217 | ||
218 | <para>Returned errors may indicate the following problems:</para> | |
219 | ||
220 | <variablelist> | |
221 | ||
222 | <varlistentry> | |
223 | <term><constant>-EUNATCH</constant></term> | |
224 | ||
225 | <listitem><para><function>sd_bus_track_remove_name()</function> or | |
226 | <function>sd_bus_track_remove_sender()</function> have been invoked for a name not previously added to the bus | |
227 | peer object.</para></listitem> | |
228 | </varlistentry> | |
229 | ||
230 | <varlistentry> | |
231 | <term><constant>-EINVAL</constant></term> | |
232 | ||
233 | <listitem><para>Specified parameter is invalid.</para></listitem> | |
234 | </varlistentry> | |
235 | ||
236 | <varlistentry> | |
237 | <term><constant>-ENOMEM</constant></term> | |
238 | ||
239 | <listitem><para>Memory allocation failed.</para></listitem> | |
240 | </varlistentry> | |
241 | ||
242 | </variablelist> | |
243 | </refsect1> | |
244 | ||
245 | <refsect1> | |
246 | <title>Notes</title> | |
247 | ||
248 | <para><function>sd_bus_track_add_name()</function> and the other calls described here are available as a shared library, | |
249 | which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry | |
250 | project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para> | |
251 | </refsect1> | |
252 | ||
253 | <refsect1> | |
254 | <title>See Also</title> | |
255 | ||
256 | <para> | |
257 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
258 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
259 | <citerefentry><refentrytitle>sd_bus_track_new</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
260 | </para> | |
261 | </refsect1> | |
262 | ||
263 | </refentry> |