1explain_fileno(3) Library Functions Manual explain_fileno(3)
2
6 explain_fileno - explain fileno(3) errors
7
9 #include <libexplain/fileno.h>
10 const char *explain_fileno(FILE *fp);
11 const char *explain_errno_fileno(int errnum, FILE *fp);
12 void explain_message_fileno(char *message, int message_size, FILE *fp);
13 void explain_message_errno_fileno(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 fileno(3) system call.
19 explain_fileno
21 const char *explain_fileno(FILE *fp);
22 The explain_fileno function is used to obtain an explanation of an
24 error returned by the fileno(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 fileno(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 if (fileno(fp) < 0)
47 {
48 fprintf(stderr, "%s\n", explain_fileno(fp));
49 exit(EXIT_FAILURE);
50 }
51 The above code example is available pre‐packaged as the
53 explain_fileno_or_die(3) function.
54 explain_errno_fileno
56 const char *explain_errno_fileno(int errnum, FILE *fp);
57 The explain_errno_fileno function is used to obtain an explanation of
59 an error returned by the fileno(3) system call. The least the message
60 will contain is the value of strerror(errno), but usually it will do
61 much better, and indicate the underlying cause in more detail.
62 errnum The error value to be decoded, usually obtained from the errno
64 global variable just before this function is called. This is
65 necessary if you need to call any code between the system call
66 to be explained and this function, because many libc functions
67 will alter the value of errno.
68 fp The original fp, exactly as passed to the fileno(3) system
70 call.
71 Returns:
73 The message explaining the error. This message buffer is shared
74 by all libexplain functions which do not supply a buffer in
75 their argument list. This will be overwritten by the next call
76 to any libexplain function which shares this buffer, including
77 other threads.
78 Note: This function is not thread safe, because it shares a return buf‐
80 fer across all threads, and many other functions in this library.
81 Example: This function is intended to be used in a fashion similar to
83 the following example:
84 if (fileno(fp) < 0)
85 {
86 int err = errno;
87 fprintf(stderr, "%s\n", explain_errno_fileno(err, fp));
88 exit(EXIT_FAILURE);
89 }
90 The above code example is available pre‐packaged as the
92 explain_fileno_or_die(3) function.
93 explain_message_fileno
95 void explain_message_fileno(char *message, int message_size, FILE *fp);
96 The explain_message_fileno function is used to obtain an explanation of
98 an error returned by the fileno(3) system call. The least the message
99 will contain is the value of strerror(errno), but usually it will do
100 much better, and indicate the underlying cause in more detail.
101 The errno global variable will be used to obtain the error value to be
103 decoded.
104 message The location in which to store the returned message. If a suit‐
106 able message return buffer is supplied, this function is thread
107 safe.
108 message_size
110 The size in bytes of the location in which to store the
111 returned message.
112 fp The original fp, exactly as passed to the fileno(3) system
114 call.
115 Example: This function is intended to be used in a fashion similar to
117 the following example:
118 if (fileno(fp) < 0)
119 {
120 char message[3000];
121 explain_message_fileno(message, sizeof(message), fp);
122 fprintf(stderr, "%s\n", message);
123 exit(EXIT_FAILURE);
124 }
125 The above code example is available pre‐packaged as the
127 explain_fileno_or_die(3) function.
128 explain_message_errno_fileno
130 void explain_message_errno_fileno(char *message, int message_size, int
131 errnum, FILE *fp);
132 The explain_message_errno_fileno function is used to obtain an explana‐
134 tion of an error returned by the fileno(3) system call. The least the
135 message will contain is the value of strerror(errno), but usually it
136 will do much better, and indicate the underlying cause in more detail.
137 message The location in which to store the returned message. If a suit‐
139 able message return buffer is supplied, this function is thread
140 safe.
141 message_size
143 The size in bytes of the location in which to store the
144 returned message.
145 errnum The error value to be decoded, usually obtained from the errno
147 global variable just before this function is called. This is
148 necessary if you need to call any code between the system call
149 to be explained and this function, because many libc functions
150 will alter the value of errno.
151 fp The original fp, exactly as passed to the fileno(3) system
153 call.
154 Example: This function is intended to be used in a fashion similar to
156 the following example:
157 if (fileno(fp) < 0)
158 {
159 int err = errno;
160 char message[3000];
161 explain_message_errno_fileno(message, sizeof(message), err,
162 fp);
163 fprintf(stderr, "%s\n", message);
164 exit(EXIT_FAILURE);
165 }
166 The above code example is available pre‐packaged as the
168 explain_fileno_or_die(3) function.
169
171 fileno(3)
172 check and reset stream status
173 explain_fileno_or_die(3)
175 check and reset stream status and report errors
176
178 libexplain version 1.4
179 Copyright (C) 2009 Peter Miller
180 explain_fileno(3)