1aio_read(3C) Standard C Library Functions aio_read(3C)
2
6 aio_read - asynchronous read from a file
7
9 #include <aio.h>
10 int aio_read(struct aiocb *aiocbp);
12
15 The aio_read() function allows the calling process to read
16 aiocbp->aio_nbytes from the file associated with aiocbp->aio_fildes
17 into the buffer pointed to by aiocbp->aio_buf. The function call
18 returns when the read request has been initiated or queued to the file
19 or device (even when the data cannot be delivered immediately). If
20 _POSIX_PRIORITIZED_IO is defined and prioritized I/O is supported for
21 this file, then the asynchronous operation is submitted at a priority
22 equal to the scheduling priority of the process minus
23 aiocbp->aio_reqprio. The aiocbp value may be used as an argument to
24 aio_error(3C) and aio_return(3C) in order to determine the error status
25 and return status, respectively, of the asynchronous operation while it
26 is proceeding. If an error condition is encountered during queuing, the
27 function call returns without having initiated or queued the request.
28 The requested operation takes place at the absolute position in the
29 file as given by aio_offset, as if lseek(2) were called immediately
30 prior to the operation with an offset equal to aio_offset and a whence
31 equal to SEEK_SET. After a successful call to enqueue an asynchronous
32 I/O operation, the value of the file offset for the file is unspeci‐
33 fied.
34 The aiocbp->aio_sigevent structure defines what asynchronous notifica‐
37 tion is to occur when the asynchronous operation completes, as speci‐
38 fied in signal.h(3HEAD).
39 The aiocbp->aio_lio_opcode field is ignored by aio_read().
42 The aiocbp argument points to an aiocb structure. If the buffer pointed
45 to by aiocbp->aio_buf or the control block pointed to by aiocbp becomes
46 an illegal address prior to asynchronous I/O completion, then the
47 behavior is undefined.
48 Simultaneous asynchronous operations using the same aiocbp produce
51 undefined results.
52 If _POSIX_SYNCHRONIZED_IO is defined and synchronized I/O is enabled on
55 the file associated with aiocbp->aio_fildes, the behavior of this func‐
56 tion is according to the definitions of synchronized I/O data integrity
57 completion and synchronized I/O file integrity completion.
58 For any system action that changes the process memory space while an
61 asynchronous I/O is outstanding to the address range being changed, the
62 result of that action is undefined.
63 For regular files, no data transfer will occur past the offset maximum
66 established in the open file description associated with
67 aiocbp->aio_fildes.
68
70 The aio_read() function returns 0 to the calling process if the I/O
71 operation is successfully queued; otherwise, the function returns −1
72 and sets errno to indicate the error.
73
75 The aio_read() function will fail if:
76 EAGAIN The requested asynchronous I/O operation was not queued due
78 to system resource limitations.
79 Each of the following conditions may be detected synchronously at the
83 time of the call to aio_read(), or asynchronously. If any of the condi‐
84 tions below are detected synchronously, the aio_read() function returns
85 -1 and sets errno to the corresponding value. If any of the conditions
86 below are detected asynchronously, the return status of the asynchro‐
87 nous operation is set to −1, and the error status of the asynchronous
88 operation will be set to the corresponding value.
89 EBADF The aiocbp->aio_fildes argument is not a valid file descrip‐
91 tor open for reading.
92 EINVAL The file offset value implied by aiocbp->aio_offset would be
95 invalid, aiocbp->aio_reqprio is not a valid value, or
96 aiocbp->aio_nbytes is an invalid value.
97 In the case that the aio_read() successfully queues the I/O operation
101 but the operation is subsequently canceled or encounters an error, the
102 return status of the asynchronous operation is one of the values nor‐
103 mally returned by the read(2) function call. In addition, the error
104 status of the asynchronous operation will be set to one of the error
105 statuses normally set by the read() function call, or one of the fol‐
106 lowing values:
107 EBADF The aiocbp->aio_fildes argument is not a valid file
109 descriptor open for reading.
110 ECANCELED The requested I/O was canceled before the I/O completed
113 due to an explicit aio_cancel(3C) request.
114 EINVAL The file offset value implied by aiocbp->aio_offset would
117 be invalid.
118 The following condition may be detected synchronously or asyn‐
122 chronously:
123 EOVERFLOW The file is a regular file, aiobcp->aio_nbytes is greater
125 than 0 and the starting offset in aiobcp->aio_offset is
126 before the end-of-file and is at or beyond the offset max‐
127 imum in the open file description associated with
128 aiocbp->aio_fildes.
129
132 For portability, the application should set aiocb->aio_reqprio to 0.
133 The aio_read() function has a transitional interface for 64-bit file
136 offsets. See lf64(5).
137
139 See attributes(5) for descriptions of the following attributes:
140 ┌─────────────────────────────┬─────────────────────────────┐
145 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
146 ├─────────────────────────────┼─────────────────────────────┤
147 │Interface Stability │Committed │
148 ├─────────────────────────────┼─────────────────────────────┤
149 │MT-Level │MT-Safe │
150 ├─────────────────────────────┼─────────────────────────────┤
151 │Standard │See standards(5). │
152 └─────────────────────────────┴─────────────────────────────┘
153
155 close(2), exec(2), exit(2), fork(2), lseek(2), read(2), write(2),
156 aio_cancel(3C), aio_return(3C), aio.h(3HEAD), lio_listio(3C), sig‐
157 info.h(3HEAD), signal.h(3HEAD), attributes(5), lf64(5), standards(5)
158SunOS 5.11 5 Feb 2008 aio_read(3C)