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AIO_WRITE(2) | System Calls Manual | AIO_WRITE(2) |
NAME¶
aio_write
—
asynchronous write to a file (REALTIME)
LIBRARY¶
Standard C Library (libc, -lc)SYNOPSIS¶
#include
<aio.h>
int
aio_write
(struct
aiocb *iocb);
DESCRIPTION¶
Theaio_write
() system call allows the
calling process to write iocb->aio_nbytes
from the buffer pointed to by
iocb->aio_buf to the descriptor
iocb->aio_fildes. The call returns
immediately after the write request has been enqueued to the descriptor; the
write may or may not have completed at the time the call returns. If the
request could not be enqueued, generally due to invalid arguments, the call
returns without having enqueued the request.
If O_APPEND
is set for
iocb->aio_fildes,
aio_write
() operations append to the file
in the same order as the calls were made. If
O_APPEND
is not set for the file
descriptor, the write operation will occur at the absolute position from the
beginning of the file plus
iocb->aio_offset.
If _POSIX_PRIORITIZED_IO
is defined, and the
descriptor supports it, then the enqueued operation is submitted at a priority
equal to that of the calling process minus
iocb->aio_reqprio.
The iocb pointer may be subsequently used as an
argument to aio_return
() and
aio_error
() in order to determine return or
error status for the enqueued operation while it is in progress.
If the request is successfully enqueued, the value of
iocb->aio_offset can be modified during
the request as context, so this value must not be referenced after the request
is enqueued.
RESTRICTIONS¶
The Asynchronous I/O Control Block structure pointed to by iocb and the buffer that the iocb->aio_buf member of that structure references must remain valid until the operation has completed. For this reason, use of auto (stack) variables for these objects is discouraged. The asynchronous I/O control buffer iocb should be zeroed before theaio_write
() system
call to avoid passing bogus context information to the kernel.
Modifications of the Asynchronous I/O Control Block structure or the buffer
contents after the request has been enqueued, but before the request has
completed, are not allowed.
If the file offset in iocb->aio_offset is
past the offset maximum for
iocb->aio_fildes, no I/O will occur.
RETURN VALUES¶
Theaio_write
() function returns the
value 0 if successful; otherwise the value -1 is returned and
the global variable errno is set to indicate
the error.
ERRORS¶
Theaio_write
() system call will fail if:
- [
EAGAIN
] - The request was not queued because of system resource limitations.
- [
ENOSYS
] - The
aio_write
() system call is not supported.
aio_write
() system call is made, or
asynchronously, at any time thereafter. If they are detected at call time,
aio_write
() returns -1 and sets
errno appropriately; otherwise the
aio_return
() system call must be called,
and will return -1, and aio_error
() must be
called to determine the actual value that would have been returned in
errno.
- [
EBADF
] - The iocb->aio_fildes argument is invalid, or is not opened for writing.
- [
EINVAL
] - The offset iocb->aio_offset is not valid, the priority specified by iocb->aio_reqprio is not a valid priority, or the number of bytes specified by iocb->aio_nbytes is not valid.
aio_return
() system call is per the
write(2) system call, and the value returned by
the aio_error
() system call is either one
of the error returns from the write(2) system
call, or one of:
- [
EBADF
] - The iocb->aio_fildes argument is invalid for writing.
- [
ECANCELED
] - The request was explicitly canceled via a call to
aio_cancel
(). - [
EINVAL
] - The offset iocb->aio_offset would be invalid.
SEE ALSO¶
aio_cancel(2), aio_error(2), aio_return(2), aio_suspend(2), aio_waitcomplete(2), siginfo(3), aio(4)STANDARDS¶
Theaio_write
() system call is expected to
conform to the IEEE Std 1003.1
(“POSIX.1”) standard.
HISTORY¶
Theaio_write
() system call first appeared in
FreeBSD 3.0.
AUTHORS¶
This manual page was written by Wes Peters ⟨wes@softweyr.com⟩.BUGS¶
Invalid information in iocb->_aiocb_private may confuse the kernel.June 2, 1999 | Debian |