1explain_readv(3) Library Functions Manual explain_readv(3)
2
6 explain_readv - explain readv(2) errors
7
9 #include <libexplain/readv.h>
10 const char *explain_readv(int fildes, const struct iovec *iov, int
11 iovcnt);
12 const char *explain_errno_readv(int errnum, int fildes, const struct
13 iovec *iov, int iovcnt);
14 void explain_message_readv(char *message, int message_size, int fildes,
15 const struct iovec *iov, int iovcnt);
16 void explain_message_errno_readv(char *message, int message_size, int
17 errnum, int fildes, const struct iovec *iov, int iovcnt);
18
20 These functions may be used to obtain explanations for errors returned
21 by the readv(2) system call.
22 explain_readv
24 const char *explain_readv(int fildes, const struct iovec *iov, int
25 iovcnt);
26 The explain_readv function is used to obtain an explanation of an error
28 returned by the readv(2) system call. The least the message will con‐
29 tain is the value of strerror(errno), but usually it will do much bet‐
30 ter, and indicate the underlying cause in more detail.
31 The errno global variable will be used to obtain the error value to be
33 decoded.
34 fildes The original fildes, exactly as passed to the readv(2) system
36 call.
37 iov The original iov, exactly as passed to the readv(2) system
39 call.
40 iovcnt The original iovcnt, exactly as passed to the readv(2) system
42 call.
43 Returns:
45 The message explaining the error. This message buffer is shared
46 by all libexplain functions which do not supply a buffer in
47 their argument list. This will be overwritten by the next call
48 to any libexplain function which shares this buffer, including
49 other threads.
50 Note: This function is not thread safe, because it shares a return buf‐
52 fer across all threads, and many other functions in this library.
53 Example: This function is intended to be used in a fashion similar to
55 the following example:
56 ssize_t result = readv(fildes, iov, iovcnt);
57 if (result < 0)
58 {
59 fprintf(stderr, "%s\n", explain_readv(fildes, iov, iovcnt));
60 exit(EXIT_FAILURE);
61 }
62 The above code example is available pre‐packaged as the
64 explain_readv_or_die(3) function.
65 explain_errno_readv
67 const char *explain_errno_readv(int errnum, int fildes, const struct
68 iovec *iov, int iovcnt);
69 The explain_errno_readv function is used to obtain an explanation of an
71 error returned by the readv(2) system call. The least the message will
72 contain is the value of strerror(errno), but usually it will do much
73 better, and indicate the underlying cause in more detail.
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 fildes The original fildes, exactly as passed to the readv(2) system
82 call.
83 iov The original iov, exactly as passed to the readv(2) system
85 call.
86 iovcnt The original iovcnt, exactly as passed to the readv(2) system
88 call.
89 Returns:
91 The message explaining the error. This message buffer is shared
92 by all libexplain functions which do not supply a buffer in
93 their argument list. This will be overwritten by the next call
94 to any libexplain function which shares this buffer, including
95 other threads.
96 Note: This function is not thread safe, because it shares a return buf‐
98 fer across all threads, and many other functions in this library.
99 Example: This function is intended to be used in a fashion similar to
101 the following example:
102 ssize_t result = readv(fildes, iov, iovcnt);
103 if (result < 0)
104 {
105 int err = errno;
106 fprintf(stderr, "%s\n", explain_errno_readv(err, fildes,
107 iov, iovcnt));
108 exit(EXIT_FAILURE);
109 }
110 The above code example is available pre‐packaged as the
112 explain_readv_or_die(3) function.
113 explain_message_readv
115 void explain_message_readv(char *message, int message_size, int fildes,
116 const struct iovec *iov, int iovcnt);
117 The explain_message_readv function is used to obtain an explanation of
119 an error returned by the readv(2) system call. The least the message
120 will contain is the value of strerror(errno), but usually it will do
121 much better, and indicate the underlying cause in more detail.
122 The errno global variable will be used to obtain the error value to be
124 decoded.
125 message The location in which to store the returned message. If a suit‐
127 able message return buffer is supplied, this function is thread
128 safe.
129 message_size
131 The size in bytes of the location in which to store the
132 returned message.
133 fildes The original fildes, exactly as passed to the readv(2) system
135 call.
136 iov The original iov, exactly as passed to the readv(2) system
138 call.
139 iovcnt The original iovcnt, exactly as passed to the readv(2) system
141 call.
142 Example: This function is intended to be used in a fashion similar to
144 the following example:
145 ssize_t result = readv(fildes, iov, iovcnt);
146 if (result < 0)
147 {
148 char message[3000];
149 explain_message_readv(message, sizeof(message), fildes, iov,
150 iovcnt);
151 fprintf(stderr, "%s\n", message);
152 exit(EXIT_FAILURE);
153 }
154 The above code example is available pre‐packaged as the
156 explain_readv_or_die(3) function.
157 explain_message_errno_readv
159 void explain_message_errno_readv(char *message, int message_size, int
160 errnum, int fildes, const struct iovec *iov, int iovcnt);
161 The explain_message_errno_readv function is used to obtain an explana‐
163 tion of an error returned by the readv(2) system call. The least the
164 message will contain is the value of strerror(errno), but usually it
165 will do much better, and indicate the underlying cause in more detail.
166 message The location in which to store the returned message. If a suit‐
168 able message return buffer is supplied, this function is thread
169 safe.
170 message_size
172 The size in bytes of the location in which to store the
173 returned message.
174 errnum The error value to be decoded, usually obtained from the errno
176 global variable just before this function is called. This is
177 necessary if you need to call any code between the system call
178 to be explained and this function, because many libc functions
179 will alter the value of errno.
180 fildes The original fildes, exactly as passed to the readv(2) system
182 call.
183 iov The original iov, exactly as passed to the readv(2) system
185 call.
186 iovcnt The original iovcnt, exactly as passed to the readv(2) system
188 call.
189 Example: This function is intended to be used in a fashion similar to
191 the following example:
192 ssize_t result = readv(fildes, iov, iovcnt);
193 if (result < 0)
194 {
195 int err = errno;
196 char message[3000];
197 explain_message_errno_readv(message, sizeof(message), err,
198 fildes, iov, iovcnt);
199 fprintf(stderr, "%s\n", message);
200 exit(EXIT_FAILURE);
201 }
202 The above code example is available pre‐packaged as the
204 explain_readv_or_die(3) function.
205
207 readv(2)
208 read data into multiple buffers
209 explain_readv_or_die(3)
211 read data into multiple buffers and report errors
212
214 libexplain version 1.4
215 Copyright (C) 2009 Peter Miller
216 explain_readv(3)