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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"> |
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4 | |
5 | <!-- | |
5de0ccff | 6 | This file is part of systemd. |
71365a77 | 7 | |
5de0ccff | 8 | Copyright 2014 Zbigniew Jędrzejewski-Szmek |
71365a77 | 9 | |
5de0ccff ZJS |
10 | systemd is free software; you can redistribute it and/or modify it |
11 | under the terms of the GNU Lesser General Public License as published by | |
12 | the Free Software Foundation; either version 2.1 of the License, or | |
13 | (at your option) any later version. | |
71365a77 | 14 | |
5de0ccff ZJS |
15 | systemd is distributed in the hope that it will be useful, but |
16 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
18 | Lesser General Public License for more details. | |
71365a77 | 19 | |
5de0ccff ZJS |
20 | You should have received a copy of the GNU Lesser General Public License |
21 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
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22 | --> |
23 | ||
48f69d8f | 24 | <refentry id="sd_bus_error"> |
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25 | |
26 | <refentryinfo> | |
27 | <title>sd_bus_error</title> | |
28 | <productname>systemd</productname> | |
29 | ||
30 | <authorgroup> | |
31 | <author> | |
32 | <contrib>A monkey with a typewriter</contrib> | |
33 | <firstname>Zbigniew</firstname> | |
34 | <surname>Jędrzejewski-Szmek</surname> | |
35 | <email>zbyszek@in.waw.pl</email> | |
36 | </author> | |
37 | </authorgroup> | |
38 | </refentryinfo> | |
39 | ||
40 | <refmeta> | |
41 | <refentrytitle>sd_bus_error</refentrytitle> | |
42 | <manvolnum>3</manvolnum> | |
43 | </refmeta> | |
44 | ||
45 | <refnamediv> | |
46 | <refname>sd_bus_error</refname> | |
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47 | <refname>SD_BUS_ERROR_MAKE_CONST</refname> |
48 | <refname>SD_BUS_ERROR_NULL</refname> | |
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49 | <refname>sd_bus_error_free</refname> |
50 | <refname>sd_bus_error_set</refname> | |
9d3e5d11 | 51 | <refname>sd_bus_error_setf</refname> |
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52 | <refname>sd_bus_error_set_const</refname> |
53 | <refname>sd_bus_error_set_errno</refname> | |
54 | <refname>sd_bus_error_set_errnof</refname> | |
9d3e5d11 | 55 | <refname>sd_bus_error_set_errnofv</refname> |
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56 | <refname>sd_bus_error_get_errno</refname> |
57 | <refname>sd_bus_error_copy</refname> | |
58 | <refname>sd_bus_error_is_set</refname> | |
59 | <refname>sd_bus_error_has_name</refname> | |
60 | ||
6bb648a1 | 61 | <refpurpose>sd-bus error handling</refpurpose> |
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62 | </refnamediv> |
63 | ||
64 | <refsynopsisdiv> | |
65 | <funcsynopsis> | |
66 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
67 | ||
68 | <funcsynopsisinfo>typedef struct { | |
69 | const char *name; | |
70 | const char *message; | |
71 | ... | |
72 | } sd_bus_error;</funcsynopsisinfo> | |
73 | ||
74 | <para> | |
75 | <constant>SD_BUS_ERROR_MAKE_CONST(<replaceable>name</replaceable>, <replaceable>message</replaceable>)</constant> | |
76 | </para> | |
77 | <para> | |
78 | <constant>SD_BUS_ERROR_NULL</constant> | |
79 | </para> | |
80 | ||
81 | <funcprototype> | |
9d3e5d11 | 82 | <funcdef>void <function>sd_bus_error_free</function></funcdef> |
71365a77 ZJS |
83 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> |
84 | </funcprototype> | |
85 | ||
86 | <funcprototype> | |
87 | <funcdef>int <function>sd_bus_error_set</function></funcdef> | |
88 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
89 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
90 | <paramdef>const char *<parameter>message</parameter></paramdef> | |
91 | </funcprototype> | |
92 | ||
93 | <funcprototype> | |
94 | <funcdef>int <function>sd_bus_error_setf</function></funcdef> | |
95 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
96 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
97 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
98 | <paramdef>...</paramdef> | |
99 | </funcprototype> | |
100 | ||
101 | <funcprototype> | |
102 | <funcdef>int <function>sd_bus_error_set_const</function></funcdef> | |
103 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
104 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
105 | <paramdef>const char *<parameter>message</parameter></paramdef> | |
106 | </funcprototype> | |
107 | ||
108 | <funcprototype> | |
109 | <funcdef>int <function>sd_bus_error_set_errno</function></funcdef> | |
110 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
111 | <paramdef>int <parameter>error</parameter></paramdef> | |
112 | </funcprototype> | |
113 | ||
114 | <funcprototype> | |
115 | <funcdef>int <function>sd_bus_error_set_errnof</function></funcdef> | |
116 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
117 | <paramdef>int <parameter>error</parameter></paramdef> | |
118 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
119 | <paramdef>...</paramdef> | |
120 | </funcprototype> | |
121 | ||
9d3e5d11 LP |
122 | <funcprototype> |
123 | <funcdef>int <function>sd_bus_error_set_errnofv</function></funcdef> | |
124 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
125 | <paramdef>int <parameter>error</parameter></paramdef> | |
126 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
127 | <paramdef>va_list ap</paramdef> | |
128 | </funcprototype> | |
129 | ||
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130 | <funcprototype> |
131 | <funcdef>int <function>sd_bus_error_get_errno</function></funcdef> | |
132 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
133 | </funcprototype> | |
134 | ||
135 | <funcprototype> | |
136 | <funcdef>int <function>sd_bus_error_copy</function></funcdef> | |
137 | <paramdef>sd_bus_error *<parameter>dst</parameter></paramdef> | |
138 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
139 | </funcprototype> | |
140 | ||
141 | <funcprototype> | |
142 | <funcdef>int <function>sd_bus_error_is_set</function></funcdef> | |
143 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
144 | </funcprototype> | |
145 | ||
146 | <funcprototype> | |
147 | <funcdef>int <function>sd_bus_error_has_name</function></funcdef> | |
148 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
149 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
150 | </funcprototype> | |
151 | </funcsynopsis> | |
152 | ||
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153 | </refsynopsisdiv> |
154 | ||
155 | <refsect1> | |
156 | <title>Description</title> | |
157 | ||
66f756d4 | 158 | <para>The <structname>sd_bus_error</structname> structure carries |
9d3e5d11 LP |
159 | information about a D-Bus error condition. The functions described |
160 | below may be used to set and query fields in this structure. The | |
161 | <structfield>name</structfield> field contains a short identifier | |
162 | of an error. It should follow the rules for error names described | |
163 | in the D-Bus specification, subsection <ulink | |
71365a77 | 164 | url="http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names">Valid |
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165 | Names</ulink>. A number of common, standardized error names are |
166 | described in | |
167 | <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
168 | but additional domain-specific errors may be defined by | |
169 | applications. The <structfield>message</structfield> field usually | |
170 | contains a human readable string describing the details, but might | |
171 | be NULL. An unset <structname>sd_bus_error</structname> structure | |
172 | should have both fields initialized to NULL. Set an error | |
173 | structure to <constant>SD_BUS_ERROR_NULL</constant> in order to | |
174 | reset both fields to NULL. When no longer necessary, resources | |
175 | held by the <structname>sd_bus_error</structname>structure should | |
176 | be destroyed with <function>sd_bus_error_free()</function>.</para> | |
177 | ||
178 | <para><function>sd_bus_error_set()</function> sets an error | |
179 | structure to the specified name and message strings. The strings | |
180 | will be copied into internal, newly allocated memory. It is | |
181 | essential to free the error structure again when it is not | |
182 | required anymore (see above). The function will return an | |
183 | <varname>errno</varname>-like negative value (see <citerefentry | |
184 | project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>) | |
185 | determined from the specified error name. Various well-known | |
186 | D-Bus errors are converted to well-known <varname>errno</varname> | |
187 | counterparts, and the other ones to <constant>-EIO</constant>. See | |
188 | <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
189 | for a list of well-known error names. Additional error mappings | |
190 | may be defined with | |
191 | <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If | |
192 | <parameter>e</parameter> is NULL no error structure is initialized | |
193 | but the error is still converted into an | |
194 | <varname>errno</varname>-style error. If | |
66f756d4 | 195 | <parameter>name</parameter> is <constant>NULL</constant>, it is |
06b643e7 | 196 | assumed that no error occurred, and 0 is returned. This means that |
71365a77 | 197 | this function may be conveniently used in a |
9d3e5d11 LP |
198 | <function>return</function> statement. If |
199 | <parameter>message</parameter> is NULL no message is set. This | |
200 | call can fail if no memory may be allocated for the name and | |
201 | message strings, in which case an | |
202 | <constant>SD_BUS_ERROR_NO_MEMORY</constant> error might be set | |
203 | instead and -ENOMEM returned. Do not use this call on error | |
204 | structures that are already initialized. If you intend to reuse an | |
205 | error structure free the old data stored in it with | |
206 | <function>sd_bus_error_free()</function> first.</para> | |
207 | ||
208 | <para><function>sd_bus_error_setf()</function> is similar to | |
209 | <function>sd_bus_error_set()</function>, but takes a <citerefentry | |
210 | project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
211 | format string and corresponding arguments to generate the | |
212 | <structfield>message</structfield> field.</para> | |
213 | ||
214 | <para><function>sd_bus_error_set_const()</function> is similar to | |
215 | <function>sd_bus_error_set()</function>, but the string parameters | |
216 | are not copied internally, and must hence remain constant and | |
217 | valid for the lifetime of <parameter>e</parameter>. Use this call | |
218 | to avoid memory allocations when setting error structures. Since | |
219 | this call does not allocate memory it will not fail with an | |
220 | out-of-memory condition, as | |
221 | <function>sd_bus_error_set()</function> can, as described | |
222 | above. Alternatively, the | |
223 | <constant>SD_BUS_ERROR_MAKE_CONST()</constant> macro may be used | |
224 | to generate a literal, constant bus error structure | |
225 | on-the-fly.</para> | |
226 | ||
227 | <para><function>sd_bus_error_set_errno()</function> will set | |
228 | <structfield>name</structfield> from an | |
229 | <varname>errno</varname>-like value that is converted to a D-Bus | |
230 | error. <citerefentry | |
231 | project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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232 | will be used to set <structfield>message</structfield>. Well-known |
233 | D-Bus error names will be used for <structfield>name</structfield> | |
9d3e5d11 LP |
234 | if applicable, otherwise a name in the |
235 | <literal>System.Error.</literal> namespace will be generated. The | |
236 | sign of the specified error number is ignored. The absolute value | |
237 | is used implicitly. The call always returns a negative value, for | |
238 | convenient usage in <function>return</function> statements. This | |
239 | call might fail due to lack of memory, in which case an | |
240 | <constant>SD_BUS_ERROR_NO_MEMORY</constant> error is set instead, | |
241 | and -ENOMEM returned.</para> | |
242 | ||
243 | <para><function>sd_bus_error_set_errnof()</function> is similar to | |
244 | <function>sd_bus_error_set_errno()</function>, but in addition to | |
245 | <parameter>error</parameter>, takes a <citerefentry | |
246 | project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
247 | format string and corresponding arguments. The | |
248 | <structfield>message</structfield> field will be generated from | |
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249 | <parameter>format</parameter> and the arguments.</para> |
250 | ||
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251 | <para><function>sd_bus_error_set_errnofv()</function> is similar to |
252 | <function>sd_bus_error_set_errnof()</function> but takes the | |
253 | format string parameters as <citerefentry | |
254 | project='man-pages'><refentrytitle>va_arg</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
255 | parameter list.</para> | |
256 | ||
257 | <para><function>sd_bus_error_get_errno()</function> converts the | |
258 | <structfield>name</structfield> field of an error structure to an | |
259 | <varname>errno</varname>-like (positive) value using the same | |
260 | rules as <function>sd_bus_error_set()</function>. If | |
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261 | <parameter>e</parameter> is <constant>NULL</constant>, 0 will be |
262 | returned.</para> | |
71365a77 | 263 | |
9d3e5d11 | 264 | <para><function>sd_bus_error_copy()</function> will initialize |
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265 | <parameter>dst</parameter> using the values in |
266 | <parameter>e</parameter>. If the strings in | |
267 | <parameter>e</parameter> were set using | |
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268 | <function>sd_bus_set_error_const()</function>, they will be shared. |
269 | Otherwise, they will be copied. Returns a converted | |
270 | <varname>errno</varname>-like, negative error code.</para> | |
71365a77 | 271 | |
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272 | <para><function>sd_bus_error_is_set()</function> will return a |
273 | non-zero value if <parameter>e</parameter> is | |
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274 | non-<constant>NULL</constant> and an error has been set, |
275 | <constant>false</constant> otherwise.</para> | |
276 | ||
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277 | <para><function>sd_bus_error_has_name()</function> will return a |
278 | non-zero value if <parameter>e</parameter> is | |
279 | non-<constant>NULL</constant> and an error with the same | |
280 | <parameter>name</parameter> has been set, | |
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281 | <constant>false</constant> otherwise.</para> |
282 | ||
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283 | <para><function>sd_bus_error_free()</function> will destroy |
284 | resources held by <parameter>e</parameter>. The parameter itself | |
285 | will not be deallocated, and must be <citerefentry | |
286 | project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>d | |
287 | by the caller if necessary. The function may also be called safely | |
288 | on unset errors (error structures with both fields set to NULL), | |
289 | in which case it performs no operation. This call will reset the | |
290 | error structure after freeing the data, so that all fields are set | |
291 | to NULL. The structure may be reused afterwards.</para> | |
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292 | </refsect1> |
293 | ||
294 | <refsect1> | |
295 | <title>Return Value</title> | |
296 | ||
9d3e5d11 LP |
297 | <para>The functions <function>sd_bus_error_set()</function>, |
298 | <function>sd_bus_error_setf()</function>, | |
299 | <function>sd_bus_error_set_const()</function>, when successful, | |
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300 | return the negative errno value corresponding to the |
301 | <parameter>name</parameter> parameter. Functions | |
9d3e5d11 LP |
302 | <function>sd_bus_error_set_errno()</function>, |
303 | <function>sd_bus_error_set_errnof()</function> and | |
304 | <function>sd_bus_error_set_errnofv()</function>, when successful, | |
305 | return the negative value of the <parameter>error</parameter> | |
306 | parameter. If an error occurs, one of the negative error values | |
307 | listed below will be returned.</para> | |
308 | ||
309 | <para><function>sd_bus_error_get_errno()</function> returns | |
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310 | <constant>false</constant> when <parameter>e</parameter> is |
311 | <constant>NULL</constant>, and a positive errno value mapped from | |
3c8fa0fd | 312 | <parameter>e->name</parameter> otherwise.</para> |
71365a77 | 313 | |
9d3e5d11 LP |
314 | <para><function>sd_bus_error_copy()</function> returns 0 or a |
315 | positive integer on success, and a negative error value converted | |
316 | from the error name otherwise.</para> | |
71365a77 | 317 | |
9d3e5d11 LP |
318 | <para><function>sd_bus_error_is_set()</function> returns a |
319 | non-zero value when <parameter>e</parameter> and the | |
320 | <structfield>name</structfield> field are | |
321 | non-<constant>NULL</constant>, zero otherwise.</para> | |
71365a77 | 322 | |
9d3e5d11 LP |
323 | <para><function>sd_bus_error_has_name()</function> returns a |
324 | non-zero value when <parameter>e</parameter> is | |
325 | non-<constant>NULL</constant> and the | |
326 | <structfield>name</structfield> field is equal to | |
327 | <parameter>name</parameter>, zero otherwise.</para> | |
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328 | </refsect1> |
329 | ||
330 | <refsect1> | |
331 | <title>Reference ownership</title> | |
332 | <para><structname>sd_bus_error</structname> is not reference | |
333 | counted. Users should destroy resources held by it by calling | |
9d3e5d11 LP |
334 | <function>sd_bus_error_free()</function>. Usually error structures |
335 | are allocated on the stack or passed in as function parameters, | |
336 | but they may also be allocated dynamically, in which case it is | |
337 | the duty of the caller to <citerefentry | |
338 | project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
339 | the memory held by the structure itself after freeing its contents | |
340 | with <function>sd_bus_error_free()</function>.</para> | |
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341 | </refsect1> |
342 | ||
343 | <refsect1> | |
344 | <title>Errors</title> | |
345 | ||
346 | <para>Returned errors may indicate the following problems:</para> | |
347 | ||
348 | <variablelist> | |
349 | ||
350 | <varlistentry> | |
8474b70c | 351 | <term><constant>-EINVAL</constant></term> |
71365a77 ZJS |
352 | |
353 | <listitem><para>Error was already set in | |
354 | <structname>sd_bus_error</structname> structure when one the | |
355 | error-setting functions was called.</para></listitem> | |
356 | </varlistentry> | |
357 | ||
358 | <varlistentry> | |
8474b70c | 359 | <term><constant>-ENOMEM</constant></term> |
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360 | |
361 | <listitem><para>Memory allocation failed.</para></listitem> | |
362 | </varlistentry> | |
363 | </variablelist> | |
364 | </refsect1> | |
365 | ||
366 | <refsect1> | |
367 | <title>Notes</title> | |
368 | ||
369 | <para><function>sd_bus_set_error()</function> and other functions | |
370 | described here are available as a shared library, which can be | |
371 | compiled and linked to with the | |
5aded369 | 372 | <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> |
71365a77 ZJS |
373 | file.</para> |
374 | </refsect1> | |
375 | ||
376 | <refsect1> | |
377 | <title>See Also</title> | |
378 | ||
379 | <para> | |
380 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
381 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
9d3e5d11 LP |
382 | <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
383 | <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
5aded369 | 384 | <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
9d3e5d11 | 385 | <citerefentry project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
71365a77 ZJS |
386 | </para> |
387 | </refsect1> | |
388 | ||
389 | </refentry> |