1explain_pipe(3) Library Functions Manual explain_pipe(3)
2
6 explain_pipe - explain pipe(2) errors
7
9 #include <libexplain/pipe.h>
10 const char *explain_pipe(int *pipefd);
11 const char *explain_errno_pipe(int errnum, int *pipefd);
12 void explain_message_pipe(char *message, int message_size, int
13 *pipefd);
14 void explain_message_errno_pipe(char *message, int message_size, int
15 errnum, int *pipefd);
16
18 These functions may be used to obtain explanations for errors returned
19 by the pipe(2) system call.
20 explain_pipe
22 const char *explain_pipe(int *pipefd);
23 The explain_pipe function is used to obtain an explanation of an error
25 returned by the pipe(2) 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 if (pipe(pipefd) < 0)
35 {
36 fprintf(stderr, "%s\n", explain_pipe(pipefd));
37 exit(EXIT_FAILURE);
38 }
39 The above code example is available pre‐packaged as the
41 explain_pipe_or_die(3) function.
42 pipefd The original pipefd, exactly as passed to the pipe(2) system
44 call.
45 Returns:
47 The message explaining the error. This message buffer is
48 shared by all libexplain functions which do not supply a buffer
49 in their argument list. This will be overwritten by the next
50 call to any libexplain function which shares this buffer,
51 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_pipe
57 const char *explain_errno_pipe(int errnum, int *pipefd);
58 The explain_errno_pipe function is used to obtain an explanation of an
60 error returned by the pipe(2) system call. The least the message will
61 contain is the value of strerror(errnum), but usually it will do much
62 better, and indicate the underlying cause in more detail.
63 This function is intended to be used in a fashion similar to the fol‐
65 lowing example:
66 if (pipe(pipefd) < 0)
67 {
68 int err = errno;
69 fprintf(stderr, "%s\n", explain_errno_pipe(err, pipefd));
70 exit(EXIT_FAILURE);
71 }
72 The above code example is available pre‐packaged as the
74 explain_pipe_or_die(3) function.
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 pipefd The original pipefd, exactly as passed to the pipe(2) system
83 call.
84 Returns:
86 The message explaining the error. This message buffer is
87 shared by all libexplain functions which do not supply a buffer
88 in their argument list. This will be overwritten by the next
89 call to any libexplain function which shares this buffer,
90 including other threads.
91 Note: This function is not thread safe, because it shares a return buf‐
93 fer across all threads, and many other functions in this library.
94 explain_message_pipe
96 void explain_message_pipe(char *message, int message_size, int
97 *pipefd);
98 The explain_message_pipe function may be used to obtain an explanation
100 of an error returned by the pipe(2) system call. The least the message
101 will contain is the value of strerror(errno), but usually it will do
102 much better, and indicate the underlying cause in more detail.
103 The errno global variable will be used to obtain the error value to be
105 decoded.
106 This function is intended to be used in a fashion similar to the fol‐
108 lowing example:
109 if (pipe(pipefd) < 0)
110 {
111 char message[3000];
112 explain_message_pipe(message, sizeof(message), pipefd);
113 fprintf(stderr, "%s\n", message);
114 exit(EXIT_FAILURE);
115 }
116 The above code example is available pre‐packaged as the
118 explain_pipe_or_die(3) function.
119 message The location in which to store the returned message. If a
121 suitable message return buffer is supplied, this function is
122 thread safe.
123 message_size
125 The size in bytes of the location in which to store the
126 returned message.
127 pipefd The original pipefd, exactly as passed to the pipe(2) system
129 call.
130 explain_message_errno_pipe
132 void explain_message_errno_pipe(char *message, int message_size, int
133 errnum, int *pipefd);
134 The explain_message_errno_pipe function may be used to obtain an expla‐
136 nation of an error returned by the pipe(2) system call. The least the
137 message will contain is the value of strerror(errnum), but usually it
138 will do much better, and indicate the underlying cause in more detail.
139 This function is intended to be used in a fashion similar to the fol‐
141 lowing example:
142 if (pipe(pipefd) < 0)
143 {
144 int err = errno;
145 char message[3000];
146 explain_message_errno_pipe(message, sizeof(message), err, pipefd);
147 fprintf(stderr, "%s\n", message);
148 exit(EXIT_FAILURE);
149 }
150 The above code example is available pre‐packaged as the
152 explain_pipe_or_die(3) function.
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 pipefd The original pipefd, exactly as passed to the pipe(2) system
169 call.
170
172 pipe(2) create pipe
173 explain_pipe_or_die(3)
175 create pipe and report errors
176
178 libexplain version 1.4
179 Copyright (C) 2009 Peter Miller
180 explain_pipe(3)