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3802a3d3 | 1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> |
71365a77 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
71365a77 ZJS |
4 | |
5 | <!-- | |
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6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
5de0ccff | 8 | This file is part of systemd. |
71365a77 | 9 | |
5de0ccff | 10 | Copyright 2014 Zbigniew Jędrzejewski-Szmek |
71365a77 | 11 | |
5de0ccff ZJS |
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. | |
71365a77 | 16 | |
5de0ccff ZJS |
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. | |
71365a77 | 21 | |
5de0ccff ZJS |
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/>. | |
71365a77 ZJS |
24 | --> |
25 | ||
48f69d8f | 26 | <refentry id="sd_bus_error"> |
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27 | |
28 | <refentryinfo> | |
29 | <title>sd_bus_error</title> | |
30 | <productname>systemd</productname> | |
31 | ||
32 | <authorgroup> | |
33 | <author> | |
34 | <contrib>A monkey with a typewriter</contrib> | |
35 | <firstname>Zbigniew</firstname> | |
36 | <surname>Jędrzejewski-Szmek</surname> | |
37 | <email>zbyszek@in.waw.pl</email> | |
38 | </author> | |
39 | </authorgroup> | |
40 | </refentryinfo> | |
41 | ||
42 | <refmeta> | |
43 | <refentrytitle>sd_bus_error</refentrytitle> | |
44 | <manvolnum>3</manvolnum> | |
45 | </refmeta> | |
46 | ||
47 | <refnamediv> | |
48 | <refname>sd_bus_error</refname> | |
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49 | <refname>SD_BUS_ERROR_MAKE_CONST</refname> |
50 | <refname>SD_BUS_ERROR_NULL</refname> | |
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51 | <refname>sd_bus_error_free</refname> |
52 | <refname>sd_bus_error_set</refname> | |
9d3e5d11 | 53 | <refname>sd_bus_error_setf</refname> |
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54 | <refname>sd_bus_error_set_const</refname> |
55 | <refname>sd_bus_error_set_errno</refname> | |
56 | <refname>sd_bus_error_set_errnof</refname> | |
9d3e5d11 | 57 | <refname>sd_bus_error_set_errnofv</refname> |
71365a77 ZJS |
58 | <refname>sd_bus_error_get_errno</refname> |
59 | <refname>sd_bus_error_copy</refname> | |
60 | <refname>sd_bus_error_is_set</refname> | |
61 | <refname>sd_bus_error_has_name</refname> | |
62 | ||
6bb648a1 | 63 | <refpurpose>sd-bus error handling</refpurpose> |
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64 | </refnamediv> |
65 | ||
66 | <refsynopsisdiv> | |
67 | <funcsynopsis> | |
68 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
69 | ||
70 | <funcsynopsisinfo>typedef struct { | |
71 | const char *name; | |
72 | const char *message; | |
1eecafb8 | 73 | … |
71365a77 ZJS |
74 | } sd_bus_error;</funcsynopsisinfo> |
75 | ||
76 | <para> | |
77 | <constant>SD_BUS_ERROR_MAKE_CONST(<replaceable>name</replaceable>, <replaceable>message</replaceable>)</constant> | |
78 | </para> | |
79 | <para> | |
80 | <constant>SD_BUS_ERROR_NULL</constant> | |
81 | </para> | |
82 | ||
83 | <funcprototype> | |
9d3e5d11 | 84 | <funcdef>void <function>sd_bus_error_free</function></funcdef> |
71365a77 ZJS |
85 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> |
86 | </funcprototype> | |
87 | ||
88 | <funcprototype> | |
89 | <funcdef>int <function>sd_bus_error_set</function></funcdef> | |
90 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
91 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
92 | <paramdef>const char *<parameter>message</parameter></paramdef> | |
93 | </funcprototype> | |
94 | ||
95 | <funcprototype> | |
96 | <funcdef>int <function>sd_bus_error_setf</function></funcdef> | |
97 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
98 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
99 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
1eecafb8 | 100 | <paramdef>…</paramdef> |
71365a77 ZJS |
101 | </funcprototype> |
102 | ||
103 | <funcprototype> | |
104 | <funcdef>int <function>sd_bus_error_set_const</function></funcdef> | |
105 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
106 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
107 | <paramdef>const char *<parameter>message</parameter></paramdef> | |
108 | </funcprototype> | |
109 | ||
110 | <funcprototype> | |
111 | <funcdef>int <function>sd_bus_error_set_errno</function></funcdef> | |
112 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
113 | <paramdef>int <parameter>error</parameter></paramdef> | |
114 | </funcprototype> | |
115 | ||
116 | <funcprototype> | |
117 | <funcdef>int <function>sd_bus_error_set_errnof</function></funcdef> | |
118 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
119 | <paramdef>int <parameter>error</parameter></paramdef> | |
120 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
1eecafb8 | 121 | <paramdef>…</paramdef> |
71365a77 ZJS |
122 | </funcprototype> |
123 | ||
9d3e5d11 LP |
124 | <funcprototype> |
125 | <funcdef>int <function>sd_bus_error_set_errnofv</function></funcdef> | |
126 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
127 | <paramdef>int <parameter>error</parameter></paramdef> | |
128 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
129 | <paramdef>va_list ap</paramdef> | |
130 | </funcprototype> | |
131 | ||
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132 | <funcprototype> |
133 | <funcdef>int <function>sd_bus_error_get_errno</function></funcdef> | |
134 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
135 | </funcprototype> | |
136 | ||
137 | <funcprototype> | |
138 | <funcdef>int <function>sd_bus_error_copy</function></funcdef> | |
139 | <paramdef>sd_bus_error *<parameter>dst</parameter></paramdef> | |
140 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
141 | </funcprototype> | |
142 | ||
143 | <funcprototype> | |
144 | <funcdef>int <function>sd_bus_error_is_set</function></funcdef> | |
145 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
146 | </funcprototype> | |
147 | ||
148 | <funcprototype> | |
149 | <funcdef>int <function>sd_bus_error_has_name</function></funcdef> | |
150 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
151 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
152 | </funcprototype> | |
153 | </funcsynopsis> | |
154 | ||
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155 | </refsynopsisdiv> |
156 | ||
157 | <refsect1> | |
158 | <title>Description</title> | |
159 | ||
66f756d4 | 160 | <para>The <structname>sd_bus_error</structname> structure carries |
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161 | information about a D-Bus error condition. The functions described |
162 | below may be used to set and query fields in this structure. The | |
163 | <structfield>name</structfield> field contains a short identifier | |
164 | of an error. It should follow the rules for error names described | |
165 | in the D-Bus specification, subsection <ulink | |
71365a77 | 166 | url="http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names">Valid |
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167 | Names</ulink>. A number of common, standardized error names are |
168 | described in | |
169 | <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
170 | but additional domain-specific errors may be defined by | |
171 | applications. The <structfield>message</structfield> field usually | |
b938cb90 | 172 | contains a human-readable string describing the details, but might |
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173 | be NULL. An unset <structname>sd_bus_error</structname> structure |
174 | should have both fields initialized to NULL. Set an error | |
175 | structure to <constant>SD_BUS_ERROR_NULL</constant> in order to | |
176 | reset both fields to NULL. When no longer necessary, resources | |
177 | held by the <structname>sd_bus_error</structname>structure should | |
178 | be destroyed with <function>sd_bus_error_free()</function>.</para> | |
179 | ||
180 | <para><function>sd_bus_error_set()</function> sets an error | |
181 | structure to the specified name and message strings. The strings | |
182 | will be copied into internal, newly allocated memory. It is | |
183 | essential to free the error structure again when it is not | |
184 | required anymore (see above). The function will return an | |
185 | <varname>errno</varname>-like negative value (see <citerefentry | |
186 | project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>) | |
187 | determined from the specified error name. Various well-known | |
188 | D-Bus errors are converted to well-known <varname>errno</varname> | |
189 | counterparts, and the other ones to <constant>-EIO</constant>. See | |
190 | <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
191 | for a list of well-known error names. Additional error mappings | |
192 | may be defined with | |
193 | <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If | |
b938cb90 | 194 | <parameter>e</parameter> is NULL, no error structure is initialized, |
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195 | but the error is still converted into an |
196 | <varname>errno</varname>-style error. If | |
66f756d4 | 197 | <parameter>name</parameter> is <constant>NULL</constant>, it is |
06b643e7 | 198 | assumed that no error occurred, and 0 is returned. This means that |
71365a77 | 199 | this function may be conveniently used in a |
9d3e5d11 | 200 | <function>return</function> statement. If |
b938cb90 | 201 | <parameter>message</parameter> is NULL, no message is set. This |
9d3e5d11 LP |
202 | call can fail if no memory may be allocated for the name and |
203 | message strings, in which case an | |
204 | <constant>SD_BUS_ERROR_NO_MEMORY</constant> error might be set | |
a8eaaee7 | 205 | instead and -ENOMEM be returned. Do not use this call on error |
9d3e5d11 | 206 | structures that are already initialized. If you intend to reuse an |
b938cb90 | 207 | error structure, free the old data stored in it with |
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208 | <function>sd_bus_error_free()</function> first.</para> |
209 | ||
210 | <para><function>sd_bus_error_setf()</function> is similar to | |
211 | <function>sd_bus_error_set()</function>, but takes a <citerefentry | |
212 | project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
213 | format string and corresponding arguments to generate the | |
214 | <structfield>message</structfield> field.</para> | |
215 | ||
216 | <para><function>sd_bus_error_set_const()</function> is similar to | |
217 | <function>sd_bus_error_set()</function>, but the string parameters | |
218 | are not copied internally, and must hence remain constant and | |
219 | valid for the lifetime of <parameter>e</parameter>. Use this call | |
220 | to avoid memory allocations when setting error structures. Since | |
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221 | this call does not allocate memory, it will not fail with an |
222 | out-of-memory condition as | |
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223 | <function>sd_bus_error_set()</function> can, as described |
224 | above. Alternatively, the | |
225 | <constant>SD_BUS_ERROR_MAKE_CONST()</constant> macro may be used | |
226 | to generate a literal, constant bus error structure | |
227 | on-the-fly.</para> | |
228 | ||
229 | <para><function>sd_bus_error_set_errno()</function> will set | |
230 | <structfield>name</structfield> from an | |
231 | <varname>errno</varname>-like value that is converted to a D-Bus | |
232 | error. <citerefentry | |
233 | project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
71365a77 ZJS |
234 | will be used to set <structfield>message</structfield>. Well-known |
235 | D-Bus error names will be used for <structfield>name</structfield> | |
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236 | if applicable, otherwise a name in the |
237 | <literal>System.Error.</literal> namespace will be generated. The | |
238 | sign of the specified error number is ignored. The absolute value | |
239 | is used implicitly. The call always returns a negative value, for | |
240 | convenient usage in <function>return</function> statements. This | |
241 | call might fail due to lack of memory, in which case an | |
242 | <constant>SD_BUS_ERROR_NO_MEMORY</constant> error is set instead, | |
a8eaaee7 | 243 | and -ENOMEM is returned.</para> |
9d3e5d11 LP |
244 | |
245 | <para><function>sd_bus_error_set_errnof()</function> is similar to | |
246 | <function>sd_bus_error_set_errno()</function>, but in addition to | |
247 | <parameter>error</parameter>, takes a <citerefentry | |
248 | project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
249 | format string and corresponding arguments. The | |
250 | <structfield>message</structfield> field will be generated from | |
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251 | <parameter>format</parameter> and the arguments.</para> |
252 | ||
9d3e5d11 | 253 | <para><function>sd_bus_error_set_errnofv()</function> is similar to |
b938cb90 | 254 | <function>sd_bus_error_set_errnof()</function>, but takes the |
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255 | format string parameters as <citerefentry |
256 | project='man-pages'><refentrytitle>va_arg</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
257 | parameter list.</para> | |
258 | ||
259 | <para><function>sd_bus_error_get_errno()</function> converts the | |
260 | <structfield>name</structfield> field of an error structure to an | |
261 | <varname>errno</varname>-like (positive) value using the same | |
262 | rules as <function>sd_bus_error_set()</function>. If | |
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263 | <parameter>e</parameter> is <constant>NULL</constant>, 0 will be |
264 | returned.</para> | |
71365a77 | 265 | |
9d3e5d11 | 266 | <para><function>sd_bus_error_copy()</function> will initialize |
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267 | <parameter>dst</parameter> using the values in |
268 | <parameter>e</parameter>. If the strings in | |
269 | <parameter>e</parameter> were set using | |
78c1edd1 | 270 | <function>sd_bus_error_set_const()</function>, they will be shared. |
9d3e5d11 LP |
271 | Otherwise, they will be copied. Returns a converted |
272 | <varname>errno</varname>-like, negative error code.</para> | |
71365a77 | 273 | |
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274 | <para><function>sd_bus_error_is_set()</function> will return a |
275 | non-zero value if <parameter>e</parameter> is | |
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276 | non-<constant>NULL</constant> and an error has been set, |
277 | <constant>false</constant> otherwise.</para> | |
278 | ||
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279 | <para><function>sd_bus_error_has_name()</function> will return a |
280 | non-zero value if <parameter>e</parameter> is | |
281 | non-<constant>NULL</constant> and an error with the same | |
282 | <parameter>name</parameter> has been set, | |
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283 | <constant>false</constant> otherwise.</para> |
284 | ||
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285 | <para><function>sd_bus_error_free()</function> will destroy |
286 | resources held by <parameter>e</parameter>. The parameter itself | |
287 | will not be deallocated, and must be <citerefentry | |
288 | project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>d | |
289 | by the caller if necessary. The function may also be called safely | |
290 | on unset errors (error structures with both fields set to NULL), | |
291 | in which case it performs no operation. This call will reset the | |
292 | error structure after freeing the data, so that all fields are set | |
293 | to NULL. The structure may be reused afterwards.</para> | |
71365a77 ZJS |
294 | </refsect1> |
295 | ||
296 | <refsect1> | |
297 | <title>Return Value</title> | |
298 | ||
9d3e5d11 | 299 | <para>The functions <function>sd_bus_error_set()</function>, |
a8eaaee7 | 300 | <function>sd_bus_error_setf()</function>, and |
9d3e5d11 | 301 | <function>sd_bus_error_set_const()</function>, when successful, |
71365a77 | 302 | return the negative errno value corresponding to the |
a8eaaee7 | 303 | <parameter>name</parameter> parameter. The functions |
9d3e5d11 LP |
304 | <function>sd_bus_error_set_errno()</function>, |
305 | <function>sd_bus_error_set_errnof()</function> and | |
306 | <function>sd_bus_error_set_errnofv()</function>, when successful, | |
307 | return the negative value of the <parameter>error</parameter> | |
308 | parameter. If an error occurs, one of the negative error values | |
309 | listed below will be returned.</para> | |
310 | ||
311 | <para><function>sd_bus_error_get_errno()</function> returns | |
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312 | <constant>false</constant> when <parameter>e</parameter> is |
313 | <constant>NULL</constant>, and a positive errno value mapped from | |
3c8fa0fd | 314 | <parameter>e->name</parameter> otherwise.</para> |
71365a77 | 315 | |
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316 | <para><function>sd_bus_error_copy()</function> returns 0 or a |
317 | positive integer on success, and a negative error value converted | |
318 | from the error name otherwise.</para> | |
71365a77 | 319 | |
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320 | <para><function>sd_bus_error_is_set()</function> returns a |
321 | non-zero value when <parameter>e</parameter> and the | |
322 | <structfield>name</structfield> field are | |
323 | non-<constant>NULL</constant>, zero otherwise.</para> | |
71365a77 | 324 | |
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325 | <para><function>sd_bus_error_has_name()</function> returns a |
326 | non-zero value when <parameter>e</parameter> is | |
327 | non-<constant>NULL</constant> and the | |
328 | <structfield>name</structfield> field is equal to | |
329 | <parameter>name</parameter>, zero otherwise.</para> | |
71365a77 ZJS |
330 | </refsect1> |
331 | ||
332 | <refsect1> | |
333 | <title>Reference ownership</title> | |
334 | <para><structname>sd_bus_error</structname> is not reference | |
335 | counted. Users should destroy resources held by it by calling | |
b938cb90 | 336 | <function>sd_bus_error_free()</function>. Usually, error structures |
9d3e5d11 LP |
337 | are allocated on the stack or passed in as function parameters, |
338 | but they may also be allocated dynamically, in which case it is | |
339 | the duty of the caller to <citerefentry | |
340 | project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
341 | the memory held by the structure itself after freeing its contents | |
342 | with <function>sd_bus_error_free()</function>.</para> | |
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343 | </refsect1> |
344 | ||
345 | <refsect1> | |
346 | <title>Errors</title> | |
347 | ||
348 | <para>Returned errors may indicate the following problems:</para> | |
349 | ||
350 | <variablelist> | |
351 | ||
352 | <varlistentry> | |
8474b70c | 353 | <term><constant>-EINVAL</constant></term> |
71365a77 ZJS |
354 | |
355 | <listitem><para>Error was already set in | |
356 | <structname>sd_bus_error</structname> structure when one the | |
357 | error-setting functions was called.</para></listitem> | |
358 | </varlistentry> | |
359 | ||
360 | <varlistentry> | |
8474b70c | 361 | <term><constant>-ENOMEM</constant></term> |
71365a77 ZJS |
362 | |
363 | <listitem><para>Memory allocation failed.</para></listitem> | |
364 | </varlistentry> | |
365 | </variablelist> | |
366 | </refsect1> | |
367 | ||
368 | <refsect1> | |
369 | <title>Notes</title> | |
370 | ||
371 | <para><function>sd_bus_set_error()</function> and other functions | |
372 | described here are available as a shared library, which can be | |
373 | compiled and linked to with the | |
5aded369 | 374 | <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> |
71365a77 ZJS |
375 | file.</para> |
376 | </refsect1> | |
377 | ||
378 | <refsect1> | |
379 | <title>See Also</title> | |
380 | ||
381 | <para> | |
382 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
383 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
9d3e5d11 LP |
384 | <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
385 | <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
5aded369 | 386 | <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
9d3e5d11 | 387 | <citerefentry project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
71365a77 ZJS |
388 | </para> |
389 | </refsect1> | |
390 | ||
391 | </refentry> |