AIO_READ(3)

NAME
aio_read - asynchronous read

SYNOPSIS

#include <aio.h>

int aio_read(struct aiocb *aiocbp);

DESCRIPTION
The aio_read() function requests an asynchronous "n = read(fd, buf, count)" with fd, buf, count given by aiocbp->aio_fildes, aiocbp->aio_buf, aiocbp->aio_nbytes, respectively. The return status n can be retrieved upon completion using aio_return(3).

The data is read starting at the absolute file offset aiocbp->aio_offset, regardless of the current file position. After this request, the value of the current file position 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).

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.

RETURN VALUE
On success, 0 is returned. On error the request is not enqueued, -1 is returned, and errno is set appropriately. If an error is first 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).

ERRORS

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, aio_nbytes are invalid.

ENOSYS
    This function is not supported.

EOVERFLOW
    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.

NOTES
It is a good idea to zero out the control block before use. This 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.

CONFORMING TO
POSIX.1-2001

SEE ALSO
aio_cancel(3), aio_error(3), aio_fsync(3), aio_return(3), aio_suspend(3), aio_write(3)