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