aio_write - asynchronous write
#include <aio.h>
int aio_write(struct aiocb *aiocbp);
Link with
-lrt.
The
aio_write() function queues the I/O request described by the buffer
pointed to by
aiocbp. This function is the asynchronous analog of
write(2). The arguments of the call
write(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.)
If
O_APPEND is not set, the data is written starting at the absolute
position
aiocbp->aio_offset, regardless of the file offset. If
O_APPEND is set, data is written at the end of the file in the same
order as
aio_write() calls are made. After the call, the value of the
file offset is unspecified.
The "asynchronous" means that this call returns as soon as the request
has been enqueued; the write 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 written to 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 detected only
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 writing.
- EFBIG
- The file is a regular file, we want to write at least one byte, but the
starting position is at or beyond the maximum offset for this file.
- EINVAL
- One or more of aio_offset, aio_reqprio, aio_nbytes
are invalid.
- ENOSYS
- aio_write() is not implemented.
The
aio_write() function is available since glibc 2.1.
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
aio_write () |
Thread safety |
MT-Safe |
POSIX.1-2001, POSIX.1-2008.
It is a good idea to zero out the control block before use. The control block
must not be changed while the write operation is in progress. The buffer area
being written out 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
undefined results.
aio_cancel(3),
aio_error(3),
aio_fsync(3),
aio_read(3),
aio_return(3),
aio_suspend(3),
lio_listio(3),
aio(7)