1explain_link(3) Library Functions Manual explain_link(3)
2
6 explain_link - explain link(2) errors
7
9 #include <libexplain/link.h>
10 const char *explain_link(const char *oldpath, const char *newpath);
11 const char *explain_errno_link(int errnum, const char *oldpath, const
12 char *newpath);
13 void explain_message_link(char *message, int message_size, const char
14 *oldpath, const char *newpath);
15 void explain_message_errno_link(char *message, int message_size, int
16 errnum, const char *oldpath, const char *newpath);
17
19 These functions may be used to obtain explanations for errors returned
20 by the link(2) system call.
21 explain_link
23 const char *explain_link(const char *oldpath, const char *newpath);
24 The explain_link function is used to obtain an explanation of an error
26 returned by the link(2) system call. The least the message will con‐
27 tain is the value of strerror(errno), but usually it will do much bet‐
28 ter, 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 if (link(oldpath, newpath) < 0)
36 {
37 fprintf(stderr, "%s\n", explain_link(oldpath, newpath));
38 exit(EXIT_FAILURE);
39 }
40 oldpath The original oldpath, exactly as passed to the link(2) system
42 call.
43 newpath The original newpath, exactly as passed to the link(2) system
45 call.
46 Returns:
48 The message explaining the error. This message buffer is
49 shared by all libexplain functions which do not supply a buffer
50 in their argument list. This will be overwritten by the next
51 call to any libexplain function which shares this buffer,
52 including other threads.
53 Note: This function is not thread safe, because it shares a return buf‐
55 fer across all threads, and many other functions in this library.
56 explain_errno_link
58 const char *explain_errno_link(int errnum, const char *oldpath, const
59 char *newpath);
60 The explain_errno_link function is used to obtain an explanation of an
62 error returned by the link(2) system call. The least the message will
63 contain is the value of strerror(errnum), but usually it will do much
64 better, and indicate the underlying cause in more detail.
65 This function is intended to be used in a fashion similar to the fol‐
67 lowing example:
68 if (link(oldpath, newpath) < 0)
69 {
70 int err = errno;
71 fprintf(stderr, "%s\n", explain_errno_link(err, oldpath, newpath));
72 exit(EXIT_FAILURE);
73 }
74 errnum The error value to be decoded, usually obtained from the errno
76 global variable just before this function is called. This is
77 necessary if you need to call any code between the system call
78 to be explained and this function, because many libc functions
79 will alter the value of errno.
80 oldpath The original oldpath, exactly as passed to the link(2) system
82 call.
83 newpath The original newpath, exactly as passed to the link(2) system
85 call.
86 Returns:
88 The message explaining the error. This message buffer is
89 shared by all libexplain functions which do not supply a buffer
90 in their argument list. This will be overwritten by the next
91 call to any libexplain function which shares this buffer,
92 including other threads.
93 Note: This function is not thread safe, because it shares a return buf‐
95 fer across all threads, and many other functions in this library.
96 explain_message_link
98 void explain_message_link(char *message, int message_size, const char
99 *oldpath, const char *newpath);
100 The explain_message_link function may be used to obtain an explanation
102 of an error returned by the link(2) system call. The least the message
103 will contain is the value of strerror(errno), but usually it will do
104 much better, and indicate the underlying cause in more detail.
105 The errno global variable will be used to obtain the error value to be
107 decoded.
108 This function is intended to be used in a fashion similar to the fol‐
110 lowing example:
111 if (link(oldpath, newpath) < 0)
112 {
113 char message[3000];
114 explain_message_link(message, sizeof(message), oldpath, newpath);
115 fprintf(stderr, "%s\n", message);
116 exit(EXIT_FAILURE);
117 }
118 message The location in which to store the returned message. If a
120 suitable message return buffer is supplied, this function is
121 thread safe.
122 message_size
124 The size in bytes of the location in which to store the
125 returned message.
126 oldpath The original oldpath, exactly as passed to the link(2) system
128 call.
129 newpath The original newpath, exactly as passed to the link(2) system
131 call.
132 explain_message_errno_link
134 void explain_message_errno_link(char *message, int message_size, int
135 errnum, const char *oldpath, const char *newpath);
136 The explain_message_errno_link function may be used to obtain an expla‐
138 nation of an error returned by the link(2) system call. The least the
139 message will contain is the value of strerror(errnum), but usually it
140 will do much better, and indicate the underlying cause in more detail.
141 This function is intended to be used in a fashion similar to the fol‐
143 lowing example:
144 if (link(oldpath, newpath) < 0)
145 {
146 int err = errno;
147 char message[3000];
148 explain_message_errno_link(message, sizeof(message), err,
149 oldpath, newpath);
150 fprintf(stderr, "%s\n", message);
151 exit(EXIT_FAILURE);
152 }
153 message The location in which to store the returned message. If a
155 suitable message return buffer is supplied, this function is
156 thread safe.
157 message_size
159 The size in bytes of the location in which to store the
160 returned message.
161 errnum The error value to be decoded, usually obtained from the errno
163 global variable just before this function is called. This is
164 necessary if you need to call any code between the system call
165 to be explained and this function, because many libc functions
166 will alter the value of errno.
167 oldpath The original oldpath, exactly as passed to the link(2) system
169 call.
170 newpath The original newpath, exactly as passed to the link(2) system
172 call.
173
175 link(2) make a new name for a file
176 explain_link_or_die(3)
178 make a new name for a file and report errors
179
181 libexplain version 1.4
182 Copyright (C) 2008 Peter Miller
183 explain_link(3)