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aio_read - asynchronous read
int aio_read(struct aiocb *aiocbp);
Link with -lrt.
The aio_read() function queues the I/O request described by the buffer
pointed to by aiocbp. This function is the asynchronous analog of
read(2). The arguments of the call
read(fd, buf, count)
correspond (in order) to the fields aio_fildes, aio_buf, and aio_nbytes
of the structure pointed to by aiocbp. (See aio(7) for a description
of the aiocb structure.)
The data is read starting at the absolute file offset
aiocbp->aio_offset, regardless of the current file offset. After the
call, the value of the current file offset is unspecified.
The "asynchronous" means that this call returns as soon as the request
has been enqueued; the read may or may not have completed when the call
returns. One tests for completion using aio_error(3). The return
status of a completed I/O operation can be obtained aio_return(3).
Asynchronous notification of I/O completion can be obtained by setting
aiocbp->aio_sigevent appropriately; see sigevent(7) for details.
If _POSIX_PRIORITIZED_IO is defined, and this file supports it, then
the asynchronous operation is submitted at a priority equal to that of
the calling process minus aiocbp->aio_reqprio.
The field aiocbp->aio_lio_opcode is ignored.
No data is read from a regular file beyond its maximum offset.
On success, 0 is returned. On error the request is not enqueued, -1 is
returned, and errno is set appropriately. If an error is only detected
later, it will be reported via aio_return(3) (returns status -1) and
aio_error(3) (error status—whatever one would have gotten in errno,
such as EBADF).
EAGAIN Out of resources.
EBADF aio_fildes is not a valid file descriptor open for reading.
EINVAL One or more of aio_offset, aio_reqprio, or aio_nbytes are
ENOSYS This function is not supported.
The file is a regular file, we start reading before end-of-file
and want at least one byte, but the starting position is past
the maximum offset for this file.
The aio_read() function is available since glibc 2.1.
It is a good idea to zero out the control block before use. The
control block must not be changed while the read operation is in
progress. The buffer area being read into must not be accessed during
the operation or undefined results may occur. The memory areas
involved must remain valid.
Simultaneous I/O operations specifying the same aiocb structure produce
aio_cancel(3), aio_error(3), aio_fsync(3), aio_return(3),
aio_suspend(3), aio_write(3), lio_listio(3), aio(7)
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