1AIO_READ(3P) POSIX Programmer's Manual AIO_READ(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 aio_read - asynchronous read from a file (REALTIME)
13
15 #include <aio.h>
16 int aio_read(struct aiocb *aiocbp);
18
21 The aio_read() function shall read aiocbp->aio_nbytes from the file
22 associated with aiocbp->aio_fildes into the buffer pointed to by
23 aiocbp->aio_buf. The function call shall return when the read request
24 has been initiated or queued to the file or device (even when the data
25 cannot be delivered immediately).
26 If prioritized I/O is supported for this file, then the asynchronous
28 operation shall be submitted at a priority equal to the scheduling pri‐
29 ority of the process minus aiocbp->aio_reqprio.
30 The aiocbp value may be used as an argument to aio_error() and
32 aio_return() in order to determine the error status and return status,
33 respectively, of the asynchronous operation while it is proceeding. If
34 an error condition is encountered during queuing, the function call
35 shall return without having initiated or queued the request. The
36 requested operation takes place at the absolute position in the file as
37 given by aio_offset, as if lseek() were called immediately prior to the
38 operation with an offset equal to aio_offset and a whence equal to
39 SEEK_SET. After a successful call to enqueue an asynchronous I/O opera‐
40 tion, the value of the file offset for the file is unspecified.
41 The aiocbp->aio_lio_opcode field shall be ignored by aio_read().
43 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
50 undefined results.
51 If synchronized I/O is enabled on the file associated with
53 aiocbp->aio_fildes, the behavior of this function shall be according to
54 the definitions of synchronized I/O data integrity completion and syn‐
55 chronized I/O file integrity completion.
56 For any system action that changes the process memory space while an
58 asynchronous I/O is outstanding to the address range being changed, the
59 result of that action is undefined.
60 For regular files, no data transfer shall occur past the offset maximum
62 established in the open file description associated with
63 aiocbp->aio_fildes.
64
66 The aio_read() function shall return the value zero to the calling
67 process if the I/O operation is successfully queued; otherwise, the
68 function shall return the value -1 and set errno to indicate the error.
69
71 The aio_read() function shall fail if:
72 EAGAIN The requested asynchronous I/O operation was not queued due to
74 system resource limitations.
75 Each of the following conditions may be detected synchronously at the
78 time of the call to aio_read(), or asynchronously. If any of the con‐
79 ditions below are detected synchronously, the aio_read() function shall
80 return -1 and set errno to the corresponding value. If any of the con‐
81 ditions below are detected asynchronously, the return status of the
82 asynchronous operation is set to -1, and the error status of the asyn‐
83 chronous operation is set to the corresponding value.
84 EBADF The aiocbp->aio_fildes argument is not a valid file descriptor
86 open for reading.
87 EINVAL The file offset value implied by aiocbp->aio_offset would be
89 invalid, aiocbp->aio_reqprio is not a valid value, or
90 aiocbp->aio_nbytes is an invalid value.
91 In the case that the aio_read() successfully queues the I/O operation
94 but the operation is subsequently canceled or encounters an error, the
95 return status of the asynchronous operation is one of the values nor‐
96 mally returned by the read() function call. In addition, the error sta‐
97 tus of the asynchronous operation is set to one of the error statuses
98 normally set by the read() function call, or one of the following val‐
99 ues:
100 EBADF The aiocbp->aio_fildes argument is not a valid file descriptor
102 open for reading.
103 ECANCELED
105 The requested I/O was canceled before the I/O completed due to
106 an explicit aio_cancel() request.
107 EINVAL The file offset value implied by aiocbp->aio_offset would be
109 invalid.
110 The following condition may be detected synchronously or asyn‐
113 chronously:
114 EOVERFLOW
116 The file is a regular file, aiobcp->aio_nbytes is greater than
117 0, and the starting offset in aiobcp->aio_offset is before the
118 end-of-file and is at or beyond the offset maximum in the open
119 file description associated with aiocbp->aio_fildes.
120 The following sections are informative.
123
125 None.
126
128 The aio_read() function is part of the Asynchronous Input and Output
129 option and need not be available on all implementations.
130
132 None.
133
135 None.
136
138 aio_cancel(), aio_error(), lio_listio(), aio_return(), aio_write(),
139 close(), exec(), exit(), fork(), lseek(), read(), the Base Definitions
140 volume of IEEE Std 1003.1-2001, <aio.h>
141
143 Portions of this text are reprinted and reproduced in electronic form
144 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
145 -- Portable Operating System Interface (POSIX), The Open Group Base
146 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
147 Electrical and Electronics Engineers, Inc and The Open Group. In the
148 event of any discrepancy between this version and the original IEEE and
149 The Open Group Standard, the original IEEE and The Open Group Standard
150 is the referee document. The original Standard can be obtained online
151 at http://www.opengroup.org/unix/online.html .
152IEEE/The Open Group 2003 AIO_READ(3P)