1explain_gethostname(3) Library Functions Manual explain_gethostname(3)
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6 explain_gethostname - explain gethostname(2) errors
7
9 #include <libexplain/gethostname.h>
10 const char *explain_gethostname(char *data, size_t data_size);
11 const char *explain_errno_gethostname(int errnum, char *data, size_t
12 data_size);
13 void explain_message_gethostname(char *message, int message_size, char
14 *data, size_t data_size);
15 void explain_message_errno_gethostname(char *message, int message_size,
16 int errnum, char *data, size_t data_size);
17
19 These functions may be used to obtain explanations for errors returned
20 by the gethostname(2) system call.
21 explain_gethostname
23 const char *explain_gethostname(char *data, size_t data_size);
24 The explain_gethostname function is used to obtain an explanation of an
26 error returned by the gethostname(2) system call. The least the message
27 will contain is the value of strerror(errno), but usually it will do
28 much better, and indicate the underlying cause in more detail.
29 The errno global variable will be used to obtain the error value to be
31 decoded.
32 This function is intended to be used in a fashion similar to the fol‐
34 lowing example:
35 if (gethostname(data, data_size) < 0)
36 {
37 fprintf(stderr, "%s\n", explain_gethostname(data, data_size));
38 exit(EXIT_FAILURE);
39 }
40 The above code example is available pre‐packaged as the explain_geth‐
42 ostname_or_die(3) function.
43 data The original data, exactly as passed to the gethostname(2) sys‐
45 tem call.
46 data_size
48 The original data_size, exactly as passed to the gethostname(2)
49 system call.
50 Returns:
52 The message explaining the error. This message buffer is shared
53 by all libexplain functions which do not supply a buffer in
54 their argument list. This will be overwritten by the next call
55 to any libexplain function which shares this buffer, including
56 other threads.
57 Note: This function is not thread safe, because it shares a return buf‐
59 fer across all threads, and many other functions in this library.
60 explain_errno_gethostname
62 const char *explain_errno_gethostname(int errnum, char *data, size_t
63 data_size);
64 The explain_errno_gethostname function is used to obtain an explanation
66 of an error returned by the gethostname(2) system call. The least the
67 message will contain is the value of strerror(errno), but usually it
68 will do much better, and indicate the underlying cause in more detail.
69 This function is intended to be used in a fashion similar to the fol‐
71 lowing example:
72 if (gethostname(data, data_size) < 0)
73 {
74 int err = errno;
75 fprintf(stderr, "%s\n", explain_errno_gethostname(err, data, data_size));
76 exit(EXIT_FAILURE);
77 }
78 The above code example is available pre‐packaged as the explain_geth‐
80 ostname_or_die(3) function.
81 errnum The error value to be decoded, usually obtained from the errno
83 global variable just before this function is called. This is
84 necessary if you need to call any code between the system call
85 to be explained and this function, because many libc functions
86 will alter the value of errno.
87 data The original data, exactly as passed to the gethostname(2) sys‐
89 tem call.
90 data_size
92 The original data_size, exactly as passed to the gethostname(2)
93 system call.
94 Returns:
96 The message explaining the error. This message buffer is shared
97 by all libexplain functions which do not supply a buffer in
98 their argument list. This will be overwritten by the next call
99 to any libexplain function which shares this buffer, including
100 other threads.
101 Note: This function is not thread safe, because it shares a return buf‐
103 fer across all threads, and many other functions in this library.
104 explain_message_gethostname
106 void explain_message_gethostname(char *message, int message_size, char
107 *data, size_t data_size);
108 The explain_message_gethostname function is used to obtain an explana‐
110 tion of an error returned by the gethostname(2) system call. The least
111 the message will contain is the value of strerror(errno), but usually
112 it will do much better, and indicate the underlying cause in more
113 detail.
114 The errno global variable will be used to obtain the error value to be
116 decoded.
117 This function is intended to be used in a fashion similar to the fol‐
119 lowing example:
120 if (gethostname(data, data_size) < 0)
121 {
122 char message[3000];
123 explain_message_gethostname(message, sizeof(message), data, data_size);
124 fprintf(stderr, "%s\n", message);
125 exit(EXIT_FAILURE);
126 }
127 The above code example is available pre‐packaged as the explain_geth‐
129 ostname_or_die(3) function.
130 message The location in which to store the returned message. If a suit‐
132 able message return buffer is supplied, this function is thread
133 safe.
134 message_size
136 The size in bytes of the location in which to store the
137 returned message.
138 data The original data, exactly as passed to the gethostname(2) sys‐
140 tem call.
141 data_size
143 The original data_size, exactly as passed to the gethostname(2)
144 system call.
145 explain_message_errno_gethostname
147 void explain_message_errno_gethostname(char *message, int message_size,
148 int errnum, char *data, size_t data_size);
149 The explain_message_errno_gethostname function is used to obtain an
151 explanation of an error returned by the gethostname(2) system call.
152 The least the message will contain is the value of strerror(errno), but
153 usually it will do much better, and indicate the underlying cause in
154 more detail.
155 This function is intended to be used in a fashion similar to the fol‐
157 lowing example:
158 if (gethostname(data, data_size) < 0)
159 {
160 int err = errno;
161 char message[3000];
162 explain_message_errno_gethostname(message, sizeof(message), err, data,
163 data_size);
164 fprintf(stderr, "%s\n", message);
165 exit(EXIT_FAILURE);
166 }
167 The above code example is available pre‐packaged as the explain_geth‐
169 ostname_or_die(3) function.
170 message The location in which to store the returned message. If a suit‐
172 able message return buffer is supplied, this function is thread
173 safe.
174 message_size
176 The size in bytes of the location in which to store the
177 returned message.
178 errnum The error value to be decoded, usually obtained from the errno
180 global variable just before this function is called. This is
181 necessary if you need to call any code between the system call
182 to be explained and this function, because many libc functions
183 will alter the value of errno.
184 data The original data, exactly as passed to the gethostname(2) sys‐
186 tem call.
187 data_size
189 The original data_size, exactly as passed to the gethostname(2)
190 system call.
191
193 gethostname(2)
194 get/set hostname
195 explain_gethostname_or_die(3)
197 get/set hostname and report errors
198
200 libexplain version 1.4
201 Copyright (C) 2009 Peter Miller
202 explain_gethostname(3)