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514094f9 | 1 | <?xml version='1.0'?> |
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 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
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7 | --> |
8 | ||
7d6b2723 | 9 | <refentry id="sd_bus_error" xmlns:xi="http://www.w3.org/2001/XInclude"> |
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10 | |
11 | <refentryinfo> | |
12 | <title>sd_bus_error</title> | |
13 | <productname>systemd</productname> | |
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14 | </refentryinfo> |
15 | ||
16 | <refmeta> | |
17 | <refentrytitle>sd_bus_error</refentrytitle> | |
18 | <manvolnum>3</manvolnum> | |
19 | </refmeta> | |
20 | ||
21 | <refnamediv> | |
22 | <refname>sd_bus_error</refname> | |
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23 | <refname>SD_BUS_ERROR_MAKE_CONST</refname> |
24 | <refname>SD_BUS_ERROR_NULL</refname> | |
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25 | <refname>sd_bus_error_free</refname> |
26 | <refname>sd_bus_error_set</refname> | |
9d3e5d11 | 27 | <refname>sd_bus_error_setf</refname> |
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28 | <refname>sd_bus_error_set_const</refname> |
29 | <refname>sd_bus_error_set_errno</refname> | |
30 | <refname>sd_bus_error_set_errnof</refname> | |
9d3e5d11 | 31 | <refname>sd_bus_error_set_errnofv</refname> |
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32 | <refname>sd_bus_error_get_errno</refname> |
33 | <refname>sd_bus_error_copy</refname> | |
34 | <refname>sd_bus_error_is_set</refname> | |
35 | <refname>sd_bus_error_has_name</refname> | |
36 | ||
6bb648a1 | 37 | <refpurpose>sd-bus error handling</refpurpose> |
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38 | </refnamediv> |
39 | ||
40 | <refsynopsisdiv> | |
41 | <funcsynopsis> | |
42 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
43 | ||
44 | <funcsynopsisinfo>typedef struct { | |
45 | const char *name; | |
46 | const char *message; | |
1eecafb8 | 47 | … |
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48 | } sd_bus_error;</funcsynopsisinfo> |
49 | ||
50 | <para> | |
51 | <constant>SD_BUS_ERROR_MAKE_CONST(<replaceable>name</replaceable>, <replaceable>message</replaceable>)</constant> | |
52 | </para> | |
53 | <para> | |
54 | <constant>SD_BUS_ERROR_NULL</constant> | |
55 | </para> | |
56 | ||
57 | <funcprototype> | |
9d3e5d11 | 58 | <funcdef>void <function>sd_bus_error_free</function></funcdef> |
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59 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> |
60 | </funcprototype> | |
61 | ||
62 | <funcprototype> | |
63 | <funcdef>int <function>sd_bus_error_set</function></funcdef> | |
64 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
65 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
66 | <paramdef>const char *<parameter>message</parameter></paramdef> | |
67 | </funcprototype> | |
68 | ||
69 | <funcprototype> | |
70 | <funcdef>int <function>sd_bus_error_setf</function></funcdef> | |
71 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
72 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
73 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
1eecafb8 | 74 | <paramdef>…</paramdef> |
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75 | </funcprototype> |
76 | ||
77 | <funcprototype> | |
78 | <funcdef>int <function>sd_bus_error_set_const</function></funcdef> | |
79 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
80 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
81 | <paramdef>const char *<parameter>message</parameter></paramdef> | |
82 | </funcprototype> | |
83 | ||
84 | <funcprototype> | |
85 | <funcdef>int <function>sd_bus_error_set_errno</function></funcdef> | |
86 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
87 | <paramdef>int <parameter>error</parameter></paramdef> | |
88 | </funcprototype> | |
89 | ||
90 | <funcprototype> | |
91 | <funcdef>int <function>sd_bus_error_set_errnof</function></funcdef> | |
92 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
93 | <paramdef>int <parameter>error</parameter></paramdef> | |
94 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
1eecafb8 | 95 | <paramdef>…</paramdef> |
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96 | </funcprototype> |
97 | ||
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98 | <funcprototype> |
99 | <funcdef>int <function>sd_bus_error_set_errnofv</function></funcdef> | |
100 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
101 | <paramdef>int <parameter>error</parameter></paramdef> | |
102 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
c765233c | 103 | <paramdef>va_list <parameter>ap</parameter></paramdef> |
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104 | </funcprototype> |
105 | ||
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106 | <funcprototype> |
107 | <funcdef>int <function>sd_bus_error_get_errno</function></funcdef> | |
108 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
109 | </funcprototype> | |
110 | ||
111 | <funcprototype> | |
112 | <funcdef>int <function>sd_bus_error_copy</function></funcdef> | |
113 | <paramdef>sd_bus_error *<parameter>dst</parameter></paramdef> | |
114 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
115 | </funcprototype> | |
116 | ||
117 | <funcprototype> | |
118 | <funcdef>int <function>sd_bus_error_is_set</function></funcdef> | |
119 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
120 | </funcprototype> | |
121 | ||
122 | <funcprototype> | |
123 | <funcdef>int <function>sd_bus_error_has_name</function></funcdef> | |
124 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
125 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
126 | </funcprototype> | |
127 | </funcsynopsis> | |
128 | ||
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129 | </refsynopsisdiv> |
130 | ||
131 | <refsect1> | |
132 | <title>Description</title> | |
133 | ||
66f756d4 | 134 | <para>The <structname>sd_bus_error</structname> structure carries |
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135 | information about a D-Bus error condition. The functions described |
136 | below may be used to set and query fields in this structure. The | |
137 | <structfield>name</structfield> field contains a short identifier | |
138 | of an error. It should follow the rules for error names described | |
139 | in the D-Bus specification, subsection <ulink | |
71365a77 | 140 | url="http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names">Valid |
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141 | Names</ulink>. A number of common, standardized error names are |
142 | described in | |
143 | <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
144 | but additional domain-specific errors may be defined by | |
145 | applications. The <structfield>message</structfield> field usually | |
b938cb90 | 146 | contains a human-readable string describing the details, but might |
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147 | be NULL. An unset <structname>sd_bus_error</structname> structure |
148 | should have both fields initialized to NULL. Set an error | |
149 | structure to <constant>SD_BUS_ERROR_NULL</constant> in order to | |
150 | reset both fields to NULL. When no longer necessary, resources | |
151 | held by the <structname>sd_bus_error</structname>structure should | |
152 | be destroyed with <function>sd_bus_error_free()</function>.</para> | |
153 | ||
154 | <para><function>sd_bus_error_set()</function> sets an error | |
155 | structure to the specified name and message strings. The strings | |
156 | will be copied into internal, newly allocated memory. It is | |
157 | essential to free the error structure again when it is not | |
158 | required anymore (see above). The function will return an | |
159 | <varname>errno</varname>-like negative value (see <citerefentry | |
160 | project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>) | |
161 | determined from the specified error name. Various well-known | |
162 | D-Bus errors are converted to well-known <varname>errno</varname> | |
163 | counterparts, and the other ones to <constant>-EIO</constant>. See | |
164 | <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
165 | for a list of well-known error names. Additional error mappings | |
166 | may be defined with | |
167 | <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If | |
b938cb90 | 168 | <parameter>e</parameter> is NULL, no error structure is initialized, |
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169 | but the error is still converted into an |
170 | <varname>errno</varname>-style error. If | |
66f756d4 | 171 | <parameter>name</parameter> is <constant>NULL</constant>, it is |
06b643e7 | 172 | assumed that no error occurred, and 0 is returned. This means that |
71365a77 | 173 | this function may be conveniently used in a |
9d3e5d11 | 174 | <function>return</function> statement. If |
b938cb90 | 175 | <parameter>message</parameter> is NULL, no message is set. This |
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176 | call can fail if no memory may be allocated for the name and |
177 | message strings, in which case an | |
178 | <constant>SD_BUS_ERROR_NO_MEMORY</constant> error might be set | |
a8eaaee7 | 179 | instead and -ENOMEM be returned. Do not use this call on error |
9d3e5d11 | 180 | structures that are already initialized. If you intend to reuse an |
b938cb90 | 181 | error structure, free the old data stored in it with |
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182 | <function>sd_bus_error_free()</function> first.</para> |
183 | ||
184 | <para><function>sd_bus_error_setf()</function> is similar to | |
185 | <function>sd_bus_error_set()</function>, but takes a <citerefentry | |
186 | project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
187 | format string and corresponding arguments to generate the | |
188 | <structfield>message</structfield> field.</para> | |
189 | ||
190 | <para><function>sd_bus_error_set_const()</function> is similar to | |
191 | <function>sd_bus_error_set()</function>, but the string parameters | |
192 | are not copied internally, and must hence remain constant and | |
193 | valid for the lifetime of <parameter>e</parameter>. Use this call | |
194 | to avoid memory allocations when setting error structures. Since | |
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195 | this call does not allocate memory, it will not fail with an |
196 | out-of-memory condition as | |
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197 | <function>sd_bus_error_set()</function> can, as described |
198 | above. Alternatively, the | |
199 | <constant>SD_BUS_ERROR_MAKE_CONST()</constant> macro may be used | |
200 | to generate a literal, constant bus error structure | |
201 | on-the-fly.</para> | |
202 | ||
203 | <para><function>sd_bus_error_set_errno()</function> will set | |
204 | <structfield>name</structfield> from an | |
205 | <varname>errno</varname>-like value that is converted to a D-Bus | |
206 | error. <citerefentry | |
207 | project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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208 | will be used to set <structfield>message</structfield>. Well-known |
209 | D-Bus error names will be used for <structfield>name</structfield> | |
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210 | if applicable, otherwise a name in the |
211 | <literal>System.Error.</literal> namespace will be generated. The | |
212 | sign of the specified error number is ignored. The absolute value | |
213 | is used implicitly. The call always returns a negative value, for | |
214 | convenient usage in <function>return</function> statements. This | |
215 | call might fail due to lack of memory, in which case an | |
216 | <constant>SD_BUS_ERROR_NO_MEMORY</constant> error is set instead, | |
a8eaaee7 | 217 | and -ENOMEM is returned.</para> |
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218 | |
219 | <para><function>sd_bus_error_set_errnof()</function> is similar to | |
220 | <function>sd_bus_error_set_errno()</function>, but in addition to | |
221 | <parameter>error</parameter>, takes a <citerefentry | |
222 | project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
223 | format string and corresponding arguments. The | |
224 | <structfield>message</structfield> field will be generated from | |
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225 | <parameter>format</parameter> and the arguments.</para> |
226 | ||
9d3e5d11 | 227 | <para><function>sd_bus_error_set_errnofv()</function> is similar to |
b938cb90 | 228 | <function>sd_bus_error_set_errnof()</function>, but takes the |
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229 | format string parameters as <citerefentry |
230 | project='man-pages'><refentrytitle>va_arg</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
231 | parameter list.</para> | |
232 | ||
233 | <para><function>sd_bus_error_get_errno()</function> converts the | |
234 | <structfield>name</structfield> field of an error structure to an | |
235 | <varname>errno</varname>-like (positive) value using the same | |
236 | rules as <function>sd_bus_error_set()</function>. If | |
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237 | <parameter>e</parameter> is <constant>NULL</constant>, 0 will be |
238 | returned.</para> | |
71365a77 | 239 | |
9d3e5d11 | 240 | <para><function>sd_bus_error_copy()</function> will initialize |
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241 | <parameter>dst</parameter> using the values in |
242 | <parameter>e</parameter>. If the strings in | |
243 | <parameter>e</parameter> were set using | |
78c1edd1 | 244 | <function>sd_bus_error_set_const()</function>, they will be shared. |
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245 | Otherwise, they will be copied. Returns a converted |
246 | <varname>errno</varname>-like, negative error code.</para> | |
71365a77 | 247 | |
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248 | <para><function>sd_bus_error_is_set()</function> will return a |
249 | non-zero value if <parameter>e</parameter> is | |
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250 | non-<constant>NULL</constant> and an error has been set, |
251 | <constant>false</constant> otherwise.</para> | |
252 | ||
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253 | <para><function>sd_bus_error_has_name()</function> will return a |
254 | non-zero value if <parameter>e</parameter> is | |
255 | non-<constant>NULL</constant> and an error with the same | |
256 | <parameter>name</parameter> has been set, | |
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257 | <constant>false</constant> otherwise.</para> |
258 | ||
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259 | <para><function>sd_bus_error_free()</function> will destroy |
260 | resources held by <parameter>e</parameter>. The parameter itself | |
261 | will not be deallocated, and must be <citerefentry | |
262 | project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>d | |
263 | by the caller if necessary. The function may also be called safely | |
264 | on unset errors (error structures with both fields set to NULL), | |
265 | in which case it performs no operation. This call will reset the | |
266 | error structure after freeing the data, so that all fields are set | |
267 | to NULL. The structure may be reused afterwards.</para> | |
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268 | </refsect1> |
269 | ||
270 | <refsect1> | |
271 | <title>Return Value</title> | |
272 | ||
9d3e5d11 | 273 | <para>The functions <function>sd_bus_error_set()</function>, |
a8eaaee7 | 274 | <function>sd_bus_error_setf()</function>, and |
9d3e5d11 | 275 | <function>sd_bus_error_set_const()</function>, when successful, |
71365a77 | 276 | return the negative errno value corresponding to the |
a8eaaee7 | 277 | <parameter>name</parameter> parameter. The functions |
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278 | <function>sd_bus_error_set_errno()</function>, |
279 | <function>sd_bus_error_set_errnof()</function> and | |
280 | <function>sd_bus_error_set_errnofv()</function>, when successful, | |
281 | return the negative value of the <parameter>error</parameter> | |
282 | parameter. If an error occurs, one of the negative error values | |
283 | listed below will be returned.</para> | |
284 | ||
285 | <para><function>sd_bus_error_get_errno()</function> returns | |
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286 | <constant>false</constant> when <parameter>e</parameter> is |
287 | <constant>NULL</constant>, and a positive errno value mapped from | |
3c8fa0fd | 288 | <parameter>e->name</parameter> otherwise.</para> |
71365a77 | 289 | |
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290 | <para><function>sd_bus_error_copy()</function> returns 0 or a |
291 | positive integer on success, and a negative error value converted | |
292 | from the error name otherwise.</para> | |
71365a77 | 293 | |
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294 | <para><function>sd_bus_error_is_set()</function> returns a |
295 | non-zero value when <parameter>e</parameter> and the | |
296 | <structfield>name</structfield> field are | |
297 | non-<constant>NULL</constant>, zero otherwise.</para> | |
71365a77 | 298 | |
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299 | <para><function>sd_bus_error_has_name()</function> returns a |
300 | non-zero value when <parameter>e</parameter> is | |
301 | non-<constant>NULL</constant> and the | |
302 | <structfield>name</structfield> field is equal to | |
303 | <parameter>name</parameter>, zero otherwise.</para> | |
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304 | </refsect1> |
305 | ||
306 | <refsect1> | |
307 | <title>Reference ownership</title> | |
308 | <para><structname>sd_bus_error</structname> is not reference | |
309 | counted. Users should destroy resources held by it by calling | |
b938cb90 | 310 | <function>sd_bus_error_free()</function>. Usually, error structures |
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311 | are allocated on the stack or passed in as function parameters, |
312 | but they may also be allocated dynamically, in which case it is | |
313 | the duty of the caller to <citerefentry | |
314 | project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
315 | the memory held by the structure itself after freeing its contents | |
316 | with <function>sd_bus_error_free()</function>.</para> | |
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317 | </refsect1> |
318 | ||
319 | <refsect1> | |
320 | <title>Errors</title> | |
321 | ||
322 | <para>Returned errors may indicate the following problems:</para> | |
323 | ||
324 | <variablelist> | |
325 | ||
326 | <varlistentry> | |
8474b70c | 327 | <term><constant>-EINVAL</constant></term> |
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328 | |
329 | <listitem><para>Error was already set in | |
330 | <structname>sd_bus_error</structname> structure when one the | |
331 | error-setting functions was called.</para></listitem> | |
332 | </varlistentry> | |
333 | ||
334 | <varlistentry> | |
8474b70c | 335 | <term><constant>-ENOMEM</constant></term> |
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336 | |
337 | <listitem><para>Memory allocation failed.</para></listitem> | |
338 | </varlistentry> | |
339 | </variablelist> | |
340 | </refsect1> | |
341 | ||
7d6b2723 | 342 | <xi:include href="libsystemd-pkgconfig.xml" /> |
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343 | |
344 | <refsect1> | |
345 | <title>See Also</title> | |
346 | ||
347 | <para> | |
348 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
349 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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350 | <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
351 | <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
5aded369 | 352 | <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
9d3e5d11 | 353 | <citerefentry project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
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354 | </para> |
355 | </refsect1> | |
356 | ||
357 | </refentry> |