1AIO_READ(3) Linux Programmer's Manual AIO_READ(3)
2
6 aio_read - asynchronous read
7
9 #include <aio.h>
10 int aio_read(struct aiocb *aiocbp);
12 Link with -lrt.
14
16 The aio_read() function queues the I/O request described by the buffer
17 pointed to by aiocbp. This function is the asynchronous analog of
18 read(2). The arguments of the call
19 read(fd, buf, count)
21 correspond (in order) to the fields aio_fildes, aio_buf, and aio_nbytes
23 of the structure pointed to by aiocbp. (See aio(7) for a description
24 of the aiocb structure.)
25 The data is read starting at the absolute position aiocbp->aio_offset,
27 regardless of the file offset. After the call, the value of the file
28 offset is unspecified.
29 The "asynchronous" means that this call returns as soon as the request
31 has been enqueued; the read may or may not have completed when the call
32 returns. One tests for completion using aio_error(3). The return sta‐
33 tus of a completed I/O operation can be obtained by aio_return(3).
34 Asynchronous notification of I/O completion can be obtained by setting
35 aiocbp->aio_sigevent appropriately; see sigevent(7) for details.
36 If _POSIX_PRIORITIZED_IO is defined, and this file supports it, then
38 the asynchronous operation is submitted at a priority equal to that of
39 the calling process minus aiocbp->aio_reqprio.
40 The field aiocbp->aio_lio_opcode is ignored.
42 No data is read from a regular file beyond its maximum offset.
44
46 On success, 0 is returned. On error, the request is not enqueued, -1
47 is returned, and errno is set to indicate the error. If an error is
48 detected only later, it will be reported via aio_return(3) (returns
49 status -1) and aio_error(3) (error status—whatever one would have got‐
50 ten in errno, such as EBADF).
51
53 EAGAIN Out of resources.
54 EBADF aio_fildes is not a valid file descriptor open for reading.
56 EINVAL One or more of aio_offset, aio_reqprio, or aio_nbytes are in‐
58 valid.
59 ENOSYS aio_read() is not implemented.
61 EOVERFLOW
63 The file is a regular file, we start reading before end-of-file
64 and want at least one byte, but the starting position is past
65 the maximum offset for this file.
66
68 The aio_read() function is available since glibc 2.1.
69
71 For an explanation of the terms used in this section, see at‐
72 tributes(7).
73 ┌────────────────────────────────────────────┬───────────────┬─────────┐
75 │Interface │ Attribute │ Value │
76 ├────────────────────────────────────────────┼───────────────┼─────────┤
77 │aio_read() │ Thread safety │ MT-Safe │
78 └────────────────────────────────────────────┴───────────────┴─────────┘
79
81 POSIX.1-2001, POSIX.1-2008.
82
84 It is a good idea to zero out the control block before use. The con‐
85 trol block must not be changed while the read operation is in progress.
86 The buffer area being read into must not be accessed during the opera‐
87 tion or undefined results may occur. The memory areas involved must
88 remain valid.
89 Simultaneous I/O operations specifying the same aiocb structure produce
91 undefined results.
92
94 See aio(7).
95
97 aio_cancel(3), aio_error(3), aio_fsync(3), aio_return(3), aio_sus‐
98 pend(3), aio_write(3), lio_listio(3), aio(7)
99
101 This page is part of release 5.13 of the Linux man-pages project. A
102 description of the project, information about reporting bugs, and the
103 latest version of this page, can be found at
104 https://www.kernel.org/doc/man-pages/.
105 2021-03-22 AIO_READ(3)