1AIO_READ(P) POSIX Programmer's Manual AIO_READ(P)
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6 aio_read - asynchronous read from a file (REALTIME)
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9 #include <aio.h>
10 int aio_read(struct aiocb *aiocbp);
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15 The aio_read() function shall read aiocbp->aio_nbytes from the file
16 associated with aiocbp->aio_fildes into the buffer pointed to by
17 aiocbp->aio_buf. The function call shall return when the read request
18 has been initiated or queued to the file or device (even when the data
19 cannot be delivered immediately).
20 If prioritized I/O is supported for this file, then the asynchronous
22 operation shall be submitted at a priority equal to the scheduling pri‐
23 ority of the process minus aiocbp->aio_reqprio.
24 The aiocbp value may be used as an argument to aio_error() and
26 aio_return() in order to determine the error status and return status,
27 respectively, of the asynchronous operation while it is proceeding. If
28 an error condition is encountered during queuing, the function call
29 shall return without having initiated or queued the request. The
30 requested operation takes place at the absolute position in the file as
31 given by aio_offset, as if lseek() were called immediately prior to the
32 operation with an offset equal to aio_offset and a whence equal to
33 SEEK_SET. After a successful call to enqueue an asynchronous I/O opera‐
34 tion, the value of the file offset for the file is unspecified.
35 The aiocbp->aio_lio_opcode field shall be ignored by aio_read().
37 The aiocbp argument points to an aiocb structure. If the buffer pointed
39 to by aiocbp->aio_buf or the control block pointed to by aiocbp becomes
40 an illegal address prior to asynchronous I/O completion, then the
41 behavior is undefined.
42 Simultaneous asynchronous operations using the same aiocbp produce
44 undefined results.
45 If synchronized I/O is enabled on the file associated with
47 aiocbp->aio_fildes, the behavior of this function shall be according to
48 the definitions of synchronized I/O data integrity completion and syn‐
49 chronized I/O file integrity completion.
50 For any system action that changes the process memory space while an
52 asynchronous I/O is outstanding to the address range being changed, the
53 result of that action is undefined.
54 For regular files, no data transfer shall occur past the offset maximum
56 established in the open file description associated with
57 aiocbp->aio_fildes.
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60 The aio_read() function shall return the value zero to the calling
61 process if the I/O operation is successfully queued; otherwise, the
62 function shall return the value -1 and set errno to indicate the error.
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65 The aio_read() function shall fail if:
66 EAGAIN The requested asynchronous I/O operation was not queued due to
68 system resource limitations.
69 Each of the following conditions may be detected synchronously at the
72 time of the call to aio_read(), or asynchronously. If any of the con‐
73 ditions below are detected synchronously, the aio_read() function shall
74 return -1 and set errno to the corresponding value. If any of the con‐
75 ditions below are detected asynchronously, the return status of the
76 asynchronous operation is set to -1, and the error status of the asyn‐
77 chronous operation is set to the corresponding value.
78 EBADF The aiocbp->aio_fildes argument is not a valid file descriptor
80 open for reading.
81 EINVAL The file offset value implied by aiocbp->aio_offset would be
83 invalid, aiocbp->aio_reqprio is not a valid value, or
84 aiocbp->aio_nbytes is an invalid value.
85 In the case that the aio_read() successfully queues the I/O operation
88 but the operation is subsequently canceled or encounters an error, the
89 return status of the asynchronous operation is one of the values nor‐
90 mally returned by the read() function call. In addition, the error sta‐
91 tus of the asynchronous operation is set to one of the error statuses
92 normally set by the read() function call, or one of the following val‐
93 ues:
94 EBADF The aiocbp->aio_fildes argument is not a valid file descriptor
96 open for reading.
97 ECANCELED
99 The requested I/O was canceled before the I/O completed due to
100 an explicit aio_cancel() request.
101 EINVAL The file offset value implied by aiocbp->aio_offset would be
103 invalid.
104 The following condition may be detected synchronously or asyn‐
107 chronously:
108 EOVERFLOW
110 The file is a regular file, aiobcp->aio_nbytes is greater than
111 0, and the starting offset in aiobcp->aio_offset is before the
112 end-of-file and is at or beyond the offset maximum in the open
113 file description associated with aiocbp->aio_fildes.
114 The following sections are informative.
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119 None.
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122 The aio_read() function is part of the Asynchronous Input and Output
123 option and need not be available on all implementations.
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126 None.
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129 None.
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132 aio_cancel() , aio_error() , lio_listio() , aio_return() , aio_write()
133 , close() , exec() , exit() , fork() , lseek() , read() , the Base Def‐
134 initions volume of IEEE Std 1003.1-2001, <aio.h>
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137 Portions of this text are reprinted and reproduced in electronic form
138 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
139 -- Portable Operating System Interface (POSIX), The Open Group Base
140 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
141 Electrical and Electronics Engineers, Inc and The Open Group. In the
142 event of any discrepancy between this version and the original IEEE and
143 The Open Group Standard, the original IEEE and The Open Group Standard
144 is the referee document. The original Standard can be obtained online
145 at http://www.opengroup.org/unix/online.html .
146IEEE/The Open Group 2003 AIO_READ(P)