1explain_poll(3) Library Functions Manual explain_poll(3)
2
6 explain_poll - explain poll(2) errors
7
9 #include <libexplain/poll.h>
10 const char *explain_poll(struct pollfd *fds, int nfds, int timeout);
11 const char *explain_errno_poll(int errnum, struct pollfd *fds, int
12 nfds, int timeout);
13 void explain_message_poll(char *message, int message_size, struct
14 pollfd *fds, int nfds, int timeout);
15 void explain_message_errno_poll(char *message, int message_size, int
16 errnum, struct pollfd *fds, int nfds, int timeout);
17
19 These functions may be used to obtain explanations for errors returned
20 by the poll(2) system call.
21 explain_poll
23 const char *explain_poll(struct pollfd *fds, int nfds, int timeout);
24 The explain_poll function is used to obtain an explanation of an error
26 returned by the poll(2) system call. The least the message will contain
27 is the value of strerror(errno), but usually it will do much better,
28 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 fds The original fds, exactly as passed to the poll(2) system call.
34 nfds The original nfds, exactly as passed to the poll(2) system
36 call.
37 timeout The original timeout, exactly as passed to the poll(2) system
39 call.
40 Returns:
42 The message explaining the error. This message buffer is shared
43 by all libexplain functions which do not supply a buffer in
44 their argument list. This will be overwritten by the next call
45 to any libexplain function which shares this buffer, including
46 other threads.
47 Note: This function is not thread safe, because it shares a return buf‐
49 fer across all threads, and many other functions in this library.
50 Example: This function is intended to be used in a fashion similar to
52 the following example:
53 int result = poll(fds, nfds, timeout);
54 if (result < 0)
55 {
56 fprintf(stderr, "%s\n", explain_poll(fds, nfds, timeout));
57 exit(EXIT_FAILURE);
58 }
59 The above code example is available pre-packaged as the
61 explain_poll_or_die(3) function.
62 explain_errno_poll
64 const char *explain_errno_poll(int errnum, struct pollfd *fds, int
65 nfds, int timeout);
66 The explain_errno_poll function is used to obtain an explanation of an
68 error returned by the poll(2) system call. The least the message will
69 contain is the value of strerror(errno), but usually it will do much
70 better, and indicate the underlying cause in more detail.
71 errnum The error value to be decoded, usually obtained from the errno
73 global variable just before this function is called. This is
74 necessary if you need to call any code between the system call
75 to be explained and this function, because many libc functions
76 will alter the value of errno.
77 fds The original fds, exactly as passed to the poll(2) system call.
79 nfds The original nfds, exactly as passed to the poll(2) system
81 call.
82 timeout The original timeout, exactly as passed to the poll(2) system
84 call.
85 Returns:
87 The message explaining the error. This message buffer is shared
88 by all libexplain functions which do not supply a buffer in
89 their argument list. This will be overwritten by the next call
90 to any libexplain function which shares this buffer, including
91 other threads.
92 Note: This function is not thread safe, because it shares a return buf‐
94 fer across all threads, and many other functions in this library.
95 Example: This function is intended to be used in a fashion similar to
97 the following example:
98 int result = poll(fds, nfds, timeout);
99 if (result < 0)
100 {
101 int err = errno;
102 fprintf(stderr, "%s\n", explain_errno_poll(err, fds, nfds,
103 timeout));
104 exit(EXIT_FAILURE);
105 }
106 The above code example is available pre-packaged as the
108 explain_poll_or_die(3) function.
109 explain_message_poll
111 void explain_message_poll(char *message, int message_size, struct
112 pollfd *fds, int nfds, int timeout);
113 The explain_message_poll function is used to obtain an explanation of
115 an error returned by the poll(2) system call. The least the message
116 will contain is the value of strerror(errno), but usually it will do
117 much better, and indicate the underlying cause in more detail.
118 The errno global variable will be used to obtain the error value to be
120 decoded.
121 message The location in which to store the returned message. If a suit‐
123 able message return buffer is supplied, this function is thread
124 safe.
125 message_size
127 The size in bytes of the location in which to store the
128 returned message.
129 fds The original fds, exactly as passed to the poll(2) system call.
131 nfds The original nfds, exactly as passed to the poll(2) system
133 call.
134 timeout The original timeout, exactly as passed to the poll(2) system
136 call.
137 Example: This function is intended to be used in a fashion similar to
139 the following example:
140 int result = poll(fds, nfds, timeout);
141 if (result < 0)
142 {
143 char message[3000];
144 explain_message_poll(message, sizeof(message), fds, nfds,
145 timeout);
146 fprintf(stderr, "%s\n", message);
147 exit(EXIT_FAILURE);
148 }
149 The above code example is available pre-packaged as the
151 explain_poll_or_die(3) function.
152 explain_message_errno_poll
154 void explain_message_errno_poll(char *message, int message_size, int
155 errnum, struct pollfd *fds, int nfds, int timeout);
156 The explain_message_errno_poll function is used to obtain an explana‐
158 tion of an error returned by the poll(2) system call. The least the
159 message will contain is the value of strerror(errno), but usually it
160 will do much better, and indicate the underlying cause in more detail.
161 message The location in which to store the returned message. If a suit‐
163 able message return buffer is supplied, this function is thread
164 safe.
165 message_size
167 The size in bytes of the location in which to store the
168 returned message.
169 errnum The error value to be decoded, usually obtained from the errno
171 global variable just before this function is called. This is
172 necessary if you need to call any code between the system call
173 to be explained and this function, because many libc functions
174 will alter the value of errno.
175 fds The original fds, exactly as passed to the poll(2) system call.
177 nfds The original nfds, exactly as passed to the poll(2) system
179 call.
180 timeout The original timeout, exactly as passed to the poll(2) system
182 call.
183 Example: This function is intended to be used in a fashion similar to
185 the following example:
186 int result = poll(fds, nfds, timeout);
187 if (result < 0)
188 {
189 int err = errno;
190 char message[3000];
191 explain_message_errno_poll(message, sizeof(message), err,
192 fds, nfds, timeout);
193 fprintf(stderr, "%s\n", message);
194 exit(EXIT_FAILURE);
195 }
196 The above code example is available pre-packaged as the
198 explain_poll_or_die(3) function.
199
201 poll(2) wait for some event on a file descriptor
202 explain_poll_or_die(3)
204 wait for some event on a file descriptor and report errors
205
207 libexplain version 1.4
208 Copyright (C) 2010 Peter Miller
209 explain_poll(3)