1explain_gethostid(3) Library Functions Manual explain_gethostid(3)
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6 explain_gethostid - explain gethostid(3) errors
7
9 #include <libexplain/gethostid.h>
10 const char *explain_gethostid(void);
11 const char *explain_errno_gethostid(int errnum, void);
12 void explain_message_gethostid(char *message, int message_size, void);
13 void explain_message_errno_gethostid(char *message, int message_size,
14 int errnum, void);
15
17 These functions may be used to obtain explanations for errors returned
18 by the gethostid(3) system call.
19 explain_gethostid
21 const char *explain_gethostid(void);
22 The explain_gethostid function is used to obtain an explanation of an
24 error returned by the gethostid(3) system call. The least the message
25 will contain is the value of strerror(errno), but usually it will do
26 much better, and indicate the underlying cause in more detail.
27 The errno global variable will be used to obtain the error value to be
29 decoded.
30 Returns:
32 The message explaining the error. This message buffer is shared
33 by all libexplain functions which do not supply a buffer in
34 their argument list. This will be overwritten by the next call
35 to any libexplain function which shares this buffer, including
36 other threads.
37 Note: This function is not thread safe, because it shares a return buf‐
39 fer across all threads, and many other functions in this library.
40 Example: This function is intended to be used in a fashion similar to
42 the following example:
43 errno = 0;
44 long result = gethostid();
45 if (result < 0 || errno != 0)
46 {
47 fprintf(stderr, "%s\n", explain_gethostid());
48 exit(EXIT_FAILURE);
49 }
50 The above code example is available pre-packaged as the explain_geth‐
52 ostid_or_die(3) function.
53 explain_errno_gethostid
55 const char *explain_errno_gethostid(int errnum, void);
56 The explain_errno_gethostid function is used to obtain an explanation
58 of an error returned by the gethostid(3) system call. The least the
59 message will contain is the value of strerror(errno), but usually it
60 will do much better, and indicate the underlying cause in more detail.
61 errnum The error value to be decoded, usually obtained from the errno
63 global variable just before this function is called. This is
64 necessary if you need to call any code between the system call
65 to be explained and this function, because many libc functions
66 will alter the value of errno.
67 Returns:
69 The message explaining the error. This message buffer is shared
70 by all libexplain functions which do not supply a buffer in
71 their argument list. This will be overwritten by the next call
72 to any libexplain function which shares this buffer, including
73 other threads.
74 Note: This function is not thread safe, because it shares a return buf‐
76 fer across all threads, and many other functions in this library.
77 Example: This function is intended to be used in a fashion similar to
79 the following example:
80 errno = 0;
81 long result = gethostid();
82 if (result < 0 || errno != 0)
83 {
84 int err = errno;
85 fprintf(stderr, "%s\n", explain_errno_gethostid(err, ));
86 exit(EXIT_FAILURE);
87 }
88 The above code example is available pre-packaged as the explain_geth‐
90 ostid_or_die(3) function.
91 explain_message_gethostid
93 void explain_message_gethostid(char *message, int message_size, void);
94 The explain_message_gethostid function is used to obtain an explanation
96 of an error returned by the gethostid(3) system call. The least the
97 message will contain is the value of strerror(errno), but usually it
98 will do much better, and indicate the underlying cause in more detail.
99 The errno global variable will be used to obtain the error value to be
101 decoded.
102 message The location in which to store the returned message. If a suit‐
104 able message return buffer is supplied, this function is thread
105 safe.
106 message_size
108 The size in bytes of the location in which to store the
109 returned message.
110 Example: This function is intended to be used in a fashion similar to
112 the following example:
113 errno = 0;
114 long result = gethostid();
115 if (result < 0 || errno != 0)
116 {
117 char message[3000];
118 explain_message_gethostid(message, sizeof(message), );
119 fprintf(stderr, "%s\n", message);
120 exit(EXIT_FAILURE);
121 }
122 The above code example is available pre-packaged as the explain_geth‐
124 ostid_or_die(3) function.
125 explain_message_errno_gethostid
127 void explain_message_errno_gethostid(char *message, int message_size,
128 int errnum, void);
129 The explain_message_errno_gethostid function is used to obtain an
131 explanation of an error returned by the gethostid(3) system call. The
132 least the message will contain is the value of strerror(errno), but
133 usually it will do much better, and indicate the underlying cause in
134 more detail.
135 message The location in which to store the returned message. If a suit‐
137 able message return buffer is supplied, this function is thread
138 safe.
139 message_size
141 The size in bytes of the location in which to store the
142 returned message.
143 errnum The error value to be decoded, usually obtained from the errno
145 global variable just before this function is called. This is
146 necessary if you need to call any code between the system call
147 to be explained and this function, because many libc functions
148 will alter the value of errno.
149 Example: This function is intended to be used in a fashion similar to
151 the following example:
152 errno = 0;
153 long result = gethostid();
154 if (result < 0 || errno != 0)
155 {
156 int err = errno;
157 char message[3000];
158 explain_message_errno_gethostid(message, sizeof(message),
159 err, );
160 fprintf(stderr, "%s\n", message);
161 exit(EXIT_FAILURE);
162 }
163 The above code example is available pre-packaged as the explain_geth‐
165 ostid_or_die(3) function.
166
168 gethostid(3)
169 get the unique identifier of the current host
170 explain_gethostid_or_die(3)
172 get the unique identifier of the current host and report errors
173
175 libexplain version 1.4
176 Copyright (C) 2013 Peter Miller
177 explain_gethostid(3)