1explain_ftello(3) Library Functions Manual explain_ftello(3)
2
6 explain_ftello - explain ftello(3) errors
7
9 #include <libexplain/ftello.h>
10 const char *explain_ftello(FILE *fp);
11 const char *explain_errno_ftello(int errnum, FILE *fp);
12 void explain_message_ftello(char *message, int message_size, FILE *fp);
13 void explain_message_errno_ftello(char *message, int message_size, int
14 errnum, FILE *fp);
15
17 These functions may be used to obtain explanations for errors returned
18 by the ftello(3) system call.
19 explain_ftello
21 const char *explain_ftello(FILE *fp);
22 The explain_ftello function is used to obtain an explanation of an
24 error returned by the ftello(3) system call. The least the message will
25 contain is the value of strerror(errno), but usually it will do much
26 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 fp The original fp, exactly as passed to the ftello(3) system
32 call.
33 Returns:
35 The message explaining the error. This message buffer is shared
36 by all libexplain functions which do not supply a buffer in
37 their argument list. This will be overwritten by the next call
38 to any libexplain function which shares this buffer, including
39 other threads.
40 Note: This function is not thread safe, because it shares a return buf‐
42 fer across all threads, and many other functions in this library.
43 Example: This function is intended to be used in a fashion similar to
45 the following example:
46 off_t result = ftello(fp);
47 if (result < 0)
48 {
49 fprintf(stderr, "%s\n", explain_ftello(fp));
50 exit(EXIT_FAILURE);
51 }
52 The above code example is available pre-packaged as the
54 explain_ftello_or_die(3) function.
55 explain_errno_ftello
57 const char *explain_errno_ftello(int errnum, FILE *fp);
58 The explain_errno_ftello function is used to obtain an explanation of
60 an error returned by the ftello(3) system call. The least the message
61 will contain is the value of strerror(errno), but usually it will do
62 much better, and indicate the underlying cause in more detail.
63 errnum The error value to be decoded, usually obtained from the errno
65 global variable just before this function is called. This is
66 necessary if you need to call any code between the system call
67 to be explained and this function, because many libc functions
68 will alter the value of errno.
69 fp The original fp, exactly as passed to the ftello(3) system
71 call.
72 Returns:
74 The message explaining the error. This message buffer is shared
75 by all libexplain functions which do not supply a buffer in
76 their argument list. This will be overwritten by the next call
77 to any libexplain function which shares this buffer, including
78 other threads.
79 Note: This function is not thread safe, because it shares a return buf‐
81 fer across all threads, and many other functions in this library.
82 Example: This function is intended to be used in a fashion similar to
84 the following example:
85 off_t result = ftello(fp);
86 if (result < 0)
87 {
88 int err = errno;
89 fprintf(stderr, "%s\n", explain_errno_ftello(err, fp));
90 exit(EXIT_FAILURE);
91 }
92 The above code example is available pre-packaged as the
94 explain_ftello_or_die(3) function.
95 explain_message_ftello
97 void explain_message_ftello(char *message, int message_size, FILE *fp);
98 The explain_message_ftello function is used to obtain an explanation of
100 an error returned by the ftello(3) system call. The least the message
101 will contain is the value of strerror(errno), but usually it will do
102 much better, and indicate the underlying cause in more detail.
103 The errno global variable will be used to obtain the error value to be
105 decoded.
106 message The location in which to store the returned message. If a suit‐
108 able message return buffer is supplied, this function is thread
109 safe.
110 message_size
112 The size in bytes of the location in which to store the
113 returned message.
114 fp The original fp, exactly as passed to the ftello(3) system
116 call.
117 Example: This function is intended to be used in a fashion similar to
119 the following example:
120 off_t result = ftello(fp);
121 if (result < 0)
122 {
123 char message[3000];
124 explain_message_ftello(message, sizeof(message), fp);
125 fprintf(stderr, "%s\n", message);
126 exit(EXIT_FAILURE);
127 }
128 The above code example is available pre-packaged as the
130 explain_ftello_or_die(3) function.
131 explain_message_errno_ftello
133 void explain_message_errno_ftello(char *message, int message_size, int
134 errnum, FILE *fp);
135 The explain_message_errno_ftello function is used to obtain an explana‐
137 tion of an error returned by the ftello(3) system call. The least the
138 message will contain is the value of strerror(errno), but usually it
139 will do much better, and indicate the underlying cause in more detail.
140 message The location in which to store the returned message. If a suit‐
142 able message return buffer is supplied, this function is thread
143 safe.
144 message_size
146 The size in bytes of the location in which to store the
147 returned message.
148 errnum The error value to be decoded, usually obtained from the errno
150 global variable just before this function is called. This is
151 necessary if you need to call any code between the system call
152 to be explained and this function, because many libc functions
153 will alter the value of errno.
154 fp The original fp, exactly as passed to the ftello(3) system
156 call.
157 Example: This function is intended to be used in a fashion similar to
159 the following example:
160 off_t result = ftello(fp);
161 if (result < 0)
162 {
163 int err = errno;
164 char message[3000];
165 explain_message_errno_ftello(message, sizeof(message), err,
166 fp);
167 fprintf(stderr, "%s\n", message);
168 exit(EXIT_FAILURE);
169 }
170 The above code example is available pre-packaged as the
172 explain_ftello_or_die(3) function.
173
175 ftello(3)
176 get stream position
177 explain_ftello_or_die(3)
179 get stream position and report errors
180
182 libexplain version 1.4
183 Copyright (C) 2013 Peter Miller
184 explain_ftello(3)