AIO_WRITE(3C)AIO_WRITE(3C)NAMEaio_write - asynchronous write to a file
int aio_write(struct aiocb *aiocbp);
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 submit‐
ted 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
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 notifica‐
tion is to occur when the asynchronous operation completes, as speci‐
fied in signal.h(3HEAD).
The aiocbp→aio_lio_opcode field is ignored by aio_write().
Simultaneous asynchronous operations using the same aiocbp produce
If _POSIX_SYNCHRONIZED_IO is defined and synchronized I/O is enabled on
the file associated with aiocbp→aio_fildes, the behavior of this func‐
tion 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
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.
The aio_write() function will fail if:
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 con‐
ditions 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 asyn‐
chronous operation will be set to the corresponding value.
The aiocbp→aio_fildes argument is not a valid file descriptor
open for writing.
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 val‐
ues 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
The aiocbp→aio_fildes argument is not a valid file
descriptor open for writing.
The file offset value implied by aiocbp->aio_offset would
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 asyn‐
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
The aio_write() function has a transitional interface for 64-bit file
offsets. See lf64(5).
See attributes(5) for descriptions of the following attributes:
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
│Interface Stability │ Committed │
│MT-Level │ MT-Safe │
│Standard │ See standards(5). │
SEE ALSOaio_cancel(3C), aio_error(3C), aio_read(3C), aio_return(3C), lio_lis‐
tio(3C), close(2), _Exit(2), fork(2), lseek(2), write(2), aio.h(3HEAD),
signal.h(3HEAD), attributes(5), lf64(5), standards(5)
Feb 5, 2008 AIO_WRITE(3C)