Tribblix: manual page: aio

AIO_WRITE(3C) Standard C Library Functions AIO_WRITE(3C)

NAME

aio_write - asynchronous write to a file

SYNOPSIS

#include <aio.h>

int aio_write(struct aiocb *aiocbp);

DESCRIPTION

The aio_write() function allows the calling process to write
aiocbp->aio_nbytes to the file associated with aiocbp->aio_fildes
from the buffer pointed to by aiocbp->aio_buf. The function call
returns when the write request has been initiated or, at a minimum,
queued to the file or device. If _POSIX_PRIORITIZED_IO is defined and
prioritized I/O is supported for this file, then the asynchronous
operation is submitted at a priority equal to the scheduling priority
of the process minus aiocbp->aio_reqprio. The aiocbp may be used as
an argument to aio_error(3C) and aio_return(3C) in order to determine
the error status and return status, respectively, of the asynchronous
operation while it is proceeding.

The aiocbp argument points to an aiocb structure. If the buffer
pointed to by aiocbp->aio_buf or the control block pointed to by
aiocbp becomes an illegal address prior to asynchronous I/O
completion, then the behavior is undefined.

If O_APPEND is not set for the file descriptor aio_fildes, then the
requested operation takes place at the absolute position in the file
as given by aio_offset, as if lseek(2) were called immediately prior
to the operation with an offset equal to aio_offset and a whence
equal to SEEK_SET. If O_APPEND is set for the file descriptor, write
operations append to the file in the same order as the calls were
made. After a successful call to enqueue an asynchronous I/O
operation, the value of the file offset for the file is unspecified.

The aiocbp->aio_sigevent structure defines what asynchronous
notification is to occur when the asynchronous operation completes,
as specified in signal.h(3HEAD).

The aiocbp->aio_lio_opcode field is ignored by aio_write().

Simultaneous asynchronous operations using the same aiocbp produce
undefined results.

If _POSIX_SYNCHRONIZED_IO is defined and synchronized I/O is enabled
on the file associated with aiocbp->aio_fildes, the behavior of this
function shall be according to the definitions of synchronized I/O
data integrity completion and synchronized I/O file integrity
completion.

For any system action that changes the process memory space while an
asynchronous I/O is outstanding to the address range being changed,
the result of that action is undefined.

For regular files, no data transfer will occur past the offset
maximum established in the open file description associated with
aiocbp->aio_fildes.

RETURN VALUES

The aio_write() function returns 0 to the calling process if the I/O
operation is successfully queued; otherwise, the function returns -1
and sets errno to indicate the error.

ERRORS

The aio_write() function will fail if:

EAGAIN
The requested asynchronous I/O operation was not queued due
to system resource limitations.

Each of the following conditions may be detected synchronously at the
time of the call to aio_write(), or asynchronously. If any of the
conditions below are detected synchronously, the aio_write() function
returns -1 and sets errno to the corresponding value. If any of the
conditions below are detected asynchronously, the return status of
the asynchronous operation is set to -1, and the error status of the
asynchronous operation will be set to the corresponding value.

EBADF
The aiocbp->aio_fildes argument is not a valid file
descriptor open for writing.

EINVAL
The file offset value implied by aiocbp->aio_offset would
be invalid, aiocbp->aio_reqprio is not a valid value, or
aiocbp->aio_nbytes is an invalid value.

In the case that the aio_write() successfully queues the I/O
operation, the return status of the asynchronous operation will be
one of the values normally returned by the write(2) function call. If
the operation is successfully queued but is subsequently canceled or
encounters an error, the error status for the asynchronous operation
contains one of the values normally set by the write() function call,
or one of the following:

EBADF
The aiocbp->aio_fildes argument is not a valid file
descriptor open for writing.

EINVAL
The file offset value implied by aiocbp->aio_offset
would be invalid.

ECANCELED
The requested I/O was canceled before the I/O completed
due to an explicit aio_cancel(3C) request.

The following condition may be detected synchronously or
asynchronously:

EFBIG
The file is a regular file, aiobcp->aio_nbytes is greater
than 0 and the starting offset in aiobcp->aio_offset is at
or beyond the offset maximum in the open file description
associated with aiocbp->aio_fildes.

USAGE

The aio_write() function has a transitional interface for 64-bit file
offsets. See lf64(7).

ATTRIBUTES