1explain_fsetpos(3) Library Functions Manual explain_fsetpos(3)
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6 explain_fsetpos - explain fsetpos(3) errors
7
9 #include <libexplain/fsetpos.h>
10 const char *explain_fsetpos(FILE *fp, fpos_t *pos);
11 const char *explain_errno_fsetpos(int errnum, FILE *fp, fpos_t *pos);
12 void explain_message_fsetpos(char *message, int message_size, FILE *fp,
13 fpos_t *pos);
14 void explain_message_errno_fsetpos(char *message, int message_size, int
15 errnum, FILE *fp, fpos_t *pos);
16
18 These functions may be used to obtain explanations for errors returned
19 by the fsetpos(3) system call.
20 explain_fsetpos
22 const char *explain_fsetpos(FILE *fp, fpos_t *pos);
23 The explain_fsetpos function is used to obtain an explanation of an
25 error returned by the fsetpos(3) system call. The least the message
26 will contain is the value of strerror(errno), but usually it will do
27 much better, and indicate the underlying cause in more detail.
28 The errno global variable will be used to obtain the error value to be
30 decoded.
31 fp The original fp, exactly as passed to the fsetpos(3) system
33 call.
34 pos The original pos, exactly as passed to the fsetpos(3) system
36 call.
37 Returns:
39 The message explaining the error. This message buffer is shared
40 by all libexplain functions which do not supply a buffer in
41 their argument list. This will be overwritten by the next call
42 to any libexplain function which shares this buffer, including
43 other threads.
44 Note: This function is not thread safe, because it shares a return buf‐
46 fer across all threads, and many other functions in this library.
47 Example: This function is intended to be used in a fashion similar to
49 the following example:
50 if (fsetpos(fp, pos) < 0)
51 {
52 fprintf(stderr, "%s\n", explain_fsetpos(fp, pos));
53 exit(EXIT_FAILURE);
54 }
55 The above code example is available pre‐packaged as the explain_fset‐
57 pos_or_die(3) function.
58 explain_errno_fsetpos
60 const char *explain_errno_fsetpos(int errnum, FILE *fp, fpos_t *pos);
61 The explain_errno_fsetpos function is used to obtain an explanation of
63 an error returned by the fsetpos(3) system call. The least the message
64 will contain is the value of strerror(errno), but usually it will do
65 much better, and indicate the underlying cause in more detail.
66 errnum The error value to be decoded, usually obtained from the errno
68 global variable just before this function is called. This is
69 necessary if you need to call any code between the system call
70 to be explained and this function, because many libc functions
71 will alter the value of errno.
72 fp The original fp, exactly as passed to the fsetpos(3) system
74 call.
75 pos The original pos, exactly as passed to the fsetpos(3) system
77 call.
78 Returns:
80 The message explaining the error. This message buffer is shared
81 by all libexplain functions which do not supply a buffer in
82 their argument list. This will be overwritten by the next call
83 to any libexplain function which shares this buffer, including
84 other threads.
85 Note: This function is not thread safe, because it shares a return buf‐
87 fer across all threads, and many other functions in this library.
88 Example: This function is intended to be used in a fashion similar to
90 the following example:
91 if (fsetpos(fp, pos) < 0)
92 {
93 int err = errno;
94 fprintf(stderr, "%s\n", explain_errno_fsetpos(err, fp,
95 pos));
96 exit(EXIT_FAILURE);
97 }
98 The above code example is available pre‐packaged as the explain_fset‐
100 pos_or_die(3) function.
101 explain_message_fsetpos
103 void explain_message_fsetpos(char *message, int message_size, FILE *fp,
104 fpos_t *pos);
105 The explain_message_fsetpos function is used to obtain an explanation
107 of an error returned by the fsetpos(3) system call. The least the mes‐
108 sage will contain is the value of strerror(errno), but usually it will
109 do much better, and indicate the underlying cause in more detail.
110 The errno global variable will be used to obtain the error value to be
112 decoded.
113 message The location in which to store the returned message. If a suit‐
115 able message return buffer is supplied, this function is thread
116 safe.
117 message_size
119 The size in bytes of the location in which to store the
120 returned message.
121 fp The original fp, exactly as passed to the fsetpos(3) system
123 call.
124 pos The original pos, exactly as passed to the fsetpos(3) system
126 call.
127 Example: This function is intended to be used in a fashion similar to
129 the following example:
130 if (fsetpos(fp, pos) < 0)
131 {
132 char message[3000];
133 explain_message_fsetpos(message, sizeof(message), fp, pos);
134 fprintf(stderr, "%s\n", message);
135 exit(EXIT_FAILURE);
136 }
137 The above code example is available pre‐packaged as the explain_fset‐
139 pos_or_die(3) function.
140 explain_message_errno_fsetpos
142 void explain_message_errno_fsetpos(char *message, int message_size, int
143 errnum, FILE *fp, fpos_t *pos);
144 The explain_message_errno_fsetpos function is used to obtain an expla‐
146 nation of an error returned by the fsetpos(3) system call. The least
147 the message will contain is the value of strerror(errno), but usually
148 it will do much better, and indicate the underlying cause in more
149 detail.
150 message The location in which to store the returned message. If a suit‐
152 able message return buffer is supplied, this function is thread
153 safe.
154 message_size
156 The size in bytes of the location in which to store the
157 returned message.
158 errnum The error value to be decoded, usually obtained from the errno
160 global variable just before this function is called. This is
161 necessary if you need to call any code between the system call
162 to be explained and this function, because many libc functions
163 will alter the value of errno.
164 fp The original fp, exactly as passed to the fsetpos(3) system
166 call.
167 pos The original pos, exactly as passed to the fsetpos(3) system
169 call.
170 Example: This function is intended to be used in a fashion similar to
172 the following example:
173 if (fsetpos(fp, pos) < 0)
174 {
175 int err = errno;
176 char message[3000];
177 explain_message_errno_fsetpos(message, sizeof(message), err,
178 fp, pos);
179 fprintf(stderr, "%s\n", message);
180 exit(EXIT_FAILURE);
181 }
182 The above code example is available pre‐packaged as the explain_fset‐
184 pos_or_die(3) function.
185
187 fsetpos(3)
188 reposition a stream
189 explain_fsetpos_or_die(3)
191 reposition a stream and report errors
192
194 libexplain version 1.4
195 Copyright (C) 2010 Peter Miller
196 explain_fsetpos(3)