1explain_access(3) Library Functions Manual explain_access(3)
2
6 explain_access - explain access(2) errors
7
9 #include <libexplain/access.h>
10 const char *explain_access(const char *pathname, int mode);
11 const char *explain_errno_access(int errnum, const char *pathname, int
12 mode);
13 void explain_message_access(char *message, int message_size, const char
14 *pathname, int mode);
15 void explain_message_errno_access(char *message, int message_size, int
16 errnum, const char *pathname, int mode);
17
19 These functions may be used to obtain explanations for access(2)
20 errors.
21 explain_access
23 const char *explain_access(const char *pathname, int mode);
24 The explain_access function is used to obtain an explanation of an
26 error returned by the access(2) system call. The least the message
27 will contain is the value of strerror(errno), but usually it will do
28 much better, and indicate the underlying cause in more detail.
29 The errno global variable will be used to obtain the error value to be
31 decoded.
32 This function is intended to be used in a fashion similar to the fol‐
34 lowing example:
35 int fd = access(pathname, mode);
36 if (fd < 0)
37 {
38 fprintf(stderr, "%s0, explain_access(pathname, mode));
39 exit(EXIT_FAILURE);
40 }
41 pathname
43 The original pathname, exactly as passed to the access(2) sys‐
44 tem call.
45 mode The original mode, exactly as passed to the access(2) system
47 call. TP 8n Returns: The message explaining the error. This
48 message buffer is shared by all libexplain functions which do
49 not supply a buffer in their argument list. This will be over‐
50 written by the next call to any libexplain function which
51 shares this buffer, including other threads.
52 Note: This function is not thread safe, because it shares a return buf‐
54 fer across all threads, and many other functions in this library.
55 explain_errno_access
57 const char *explain_errno_access(int errnum, const char *pathname, int
58 mode);
59 The explain_errno_access function is used to obtain an explanation of
61 an error returned by the access(2) system call. The least the message
62 will contain is the value of strerror(errnum), but usually it will do
63 much better, and indicate the underlying cause in more detail.
64 This function is intended to be used in a fashion similar to the fol‐
66 lowing example:
67 int fd = access(pathname, mode);
68 if (fd < 0)
69 {
70 int err = errno;
71 fprintf(stderr, "%s0, explain_errno_access(err, pathname,
72 mode));
73 exit(EXIT_FAILURE);
74 }
75 errnum The error value to be decoded, usually obtained from the errno
77 global variable just before this function is called. This is
78 necessary if you need to call any code between the system call
79 to be explained and this function, because many libc functions
80 will alter the value of errno.
81 pathname
83 The original pathname, exactly as passed to the access(2) sys‐
84 tem call.
85 mode The original mode, exactly as passed to the access(2) 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_access
100 void explain_message_access(char *message, int message_size, const char
101 *pathname, int mode);
102 The explain_message_access function is used to obtain an explanation of
104 an error returned by the access(2) 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 int fd = access(pathname, mode);
114 if (fd < 0)
115 {
116 char message[3000];
117 explain_message_access(message, sizeof(message), pathname,
118 mode);
119 fprintf(stderr, "%s0, message);
120 exit(EXIT_FAILURE);
121 }
122 message The location in which to store the returned message. Because a
124 message return buffer has been supplied, this function is
125 thread safe.
126 message_size
128 The size in bytes of the location in which to store the
129 returned message.
130 pathname
132 The original pathname, exactly as passed to the access(2) sys‐
133 tem call.
134 mode The original mode, exactly as passed to the access(2) system
136 call.
137 explain_message_errno_access
139 void explain_message_errno_access(char *message, int message_size, int
140 errnum, const char *pathname, int mode);
141 The explain_message_errno_access function is used to obtain an explana‐
143 tion of an error returned by the access(2) system call. The least the
144 message will contain is the value of strerror(errnum), but usually it
145 will do much better, and indicate the underlying cause in more detail.
146 This function is intended to be used in a fashion similar to the fol‐
148 lowing exameple:
149 int fd = access(pathname, mode);
150 if (fd < 0)
151 {
152 int err = errno;
153 char message[3000];
154 explain_message_errno_access(message, sizeof(message), err,
155 pathname, mode);
156 fprintf(stderr, "%s0, message);
157 exit(EXIT_FAILURE);
158 }
159 message The location in which to store the returned message. Because a
161 message return buffer has been supplied, this function is
162 thread safe.
163 message_size
165 The size in bytes of the location in which to store the
166 returned message.
167 errnum The error value to be decoded, usually obtained from the errno
169 global variable just before this function is called. This is
170 necessary if you need to call any code between the system call
171 to be explained and this function, because many libc functions
172 will alter the value of errno.
173 pathname
175 The original pathname, exactly as passed to the access(2) sys‐
176 tem call.
177 mode The original mode, exactly as passed to the access(2) system
179 call.
180
182 libexplain version 1.4
183 Copyright (C) 2008 Peter Miller
184
186 Written by Peter Miller <pmiller@opensource.org.au>
187 explain_access(3)