1explain_fopen(3) Library Functions Manual explain_fopen(3)
2
6 explain_fopen - explain fopen(3) errors
7
9 #include <libexplain/fopen.h>
10 const char *explain_fopen(const char *path, const char *mode);
11 const char *explain_errno_fopen(int errnum, const char *path, const
12 char *mode);
13 void explain_message_fopen(char *message, int message_size, const char
14 *path, const char *mode);
15 void explain_message_errno_fopen(char *message, int message_size, int
16 errnum, const char *path, const char *mode);
17
19 These functions may be used to obtain explanations for fopen(3) errors.
20 explain_fopen
22 const char *explain_fopen(const char *path, const char *mode);
23 The explain_fopen function is used to obtain an explanation of an error
25 returned by the fopen(3) system call. The least the message will con‐
26 tain is the value of strerror(errno), but usually it will do much bet‐
27 ter, 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 This function is intended to be used in a fashion similar to the fol‐
33 lowing example:
34 FILE *fp = fopen(path, mode);
35 if (!fp)
36 {
37 const char *message = explain_fopen(path, mode);
38 fprintf(stderr, '%s0, message);
39 exit(EXIT_FAILURE);
40 }
41 path The original path, exactly as passed to the fopen(3) system
43 call.
44 mode The original mode, exactly as passed to the fopen(3) system
46 call.
47 Returns:
49 The message explaining the error. This message buffer is
50 shared by all libexplain functions which do not supply a buffer
51 in their argument list. This will be overwritten by the next
52 call to any libexplain function which shares this buffer,
53 including other threads.
54 Note: This function is not thread safe, because it shares a return buf‐
56 fer across all threads, and many other functions in this library.
57 explain_errno_fopen
59 const char *explain_errno_fopen(int errnum, const char *path, const
60 char *mode);
61 The explain_errno_fopen function is used to obtain an explanation of an
63 error returned by the fopen(3) system call. The least the message will
64 contain is the value of strerror(errno), but usually it will do much
65 better, and indicate the underlying cause in more detail.
66 This function is intended to be used in a fashion similar to the fol‐
68 lowing example:
69 FILE *fp = fopen(path, mode);
70 if (!fp)
71 {
72 const char *message = explain_errno_fopen(err, path, mode);
73 fprintf(stderr, '%s0, message);
74 exit(EXIT_FAILURE);
75 }
76 errnum The error value to be decoded, usually obtained from the errno
78 global variable just before this function is called. This is
79 necessary if you need to call any code between the system call
80 to be explained and this function, because many libc functions
81 will alter the value of errno.
82 path The original path, exactly as passed to the fopen(3) system
84 call.
85 mode The original mode, exactly as passed to the fopen(3) system
87 call.
88 Returns:
90 The message explaining the error. This message buffer is
91 shared by all libexplain functions which do not supply a buffer
92 in their argument list. This will be overwritten by the next
93 call to any libexplain function which shares this buffer,
94 including other threads.
95 Note: This function is not thread safe, because it shares a return buf‐
97 fer across all threads, and many other functions in this library.
98 explain_message_fopen
100 void explain_message_fopen(char *message, int message_size, const char
101 *path, const char *mode);
102 The explain_message_fopen function is used to obtain an explanation of
104 an error returned by the fopen(3) system call. The least the message
105 will contain is the value of strerror(errno), but usually it will do
106 much better, and indicate the underlying cause in more detail.
107 The errno global variable will be used to obtain the error value to be
109 decoded.
110 This function is intended to be used in a fashion similar to the fol‐
112 lowing example:
113 FILE *fp = fopen(path, mode);
114 if (!fp)
115 {
116 char message[3000];
117 explain_message_fopen(message, sizeof(message), path, mode);
118 fprintf(stderr, '%s0, message);
119 exit(EXIT_FAILURE);
120 }
121 message The location in which to store the returned message. Because a
123 message return buffer has been supplied, this function is
124 thread safe.
125 message_size
127 The size in bytes of the location in which to store the
128 returned message.
129 path The original path, exactly as passed to the fopen(3) system
131 call.
132 mode The original mode, exactly as passed to the fopen(3) system
134 call
135 explain_message_errno_fopen
137 void explain_message_errno_fopen(char *message, int message_size, int
138 errnum, const char *path, const char *mode);
139 The explain_message_errno_fopen function is used to obtain an explana‐
141 tion of an error returned by the fopen(3) system call. The least the
142 message will contain is the value of strerror(errno), but usually it
143 will do much better, and indicate the underlying cause in more detail.
144 This function is intended to be used in a fashion similar to the fol‐
146 lowing example:
147 FILE *fp = fopen(path, mode);
148 if (!fp)
149 {
150 int err = errno;
151 char message[3000];
152 explain_message_errno_fopen(message, sizeof(message), err, path,
153 mode);
154 fprintf(stderr, '%s0, message);
155 exit(EXIT_FAILURE);
156 }
157 message The location in which to store the returned message. Because a
159 message return buffer has been supplied, this function is
160 thread safe.
161 message_size
163 The size in bytes of the location in which to store the
164 returned message.
165 errnum The error value to be decoded, usually obtained from the errno
167 global variable just before this function is called. This is
168 necessary if you need to call any code between the system call
169 to be explained and this function, because many libc functions
170 will alter the value of errno.
171 path The original path, exactly as passed to the fopen(3) system
173 call.
174 mode The original mode, exactly as passed to the fopen(3) system
176 call.
177
179 libexplain version 1.4
180 Copyright (C) 2008 Peter Miller
181
183 Written by Peter Miller <pmiller@opensource.org.au>
184 explain_fopen(3)