aio_write (original) (raw)

The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.

A newer edition of this document exists here

NAME

aio_write - asynchronous write to a file (REALTIME)

SYNOPSIS

`[AIO] #include <aio.h>

int aio_write(struct aiocb *

aiocbp); `

DESCRIPTION

The aio_write() function shall write _aiocbp_->aio_nbytes to the file associated with_aiocbp_->aio_fildes from the buffer pointed to by _aiocbp_->aio_buf. The function shall return when the write request has been initiated or, at a minimum, queued to the file or device.

[PIO] If prioritized I/O is supported for this file, then the asynchronous operation shall be submitted at a priority equal to a base scheduling priority minus _aiocbp_->aio_reqprio. If Thread Execution Scheduling is not supported, then the base scheduling priority is that of the calling process; [PIO TPS] otherwise, the base scheduling priority is that of the calling thread.

The aiocbp argument may be used as an argument to aio_error() and aio_return() 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 shall take place at the absolute position in the file as given by aio_offset, as if lseek() 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_lio_opcode field shall be ignored by aio_write().

Simultaneous asynchronous operations using the same aiocbp produce undefined results.

[SIO] If 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 shall occur past the offset maximum established in the open file description associated with_aiocbp_->aio_fildes.

RETURN VALUE

The aio_write() function shall return the value zero if the I/O operation is successfully queued; otherwise, the function shall return the value -1 and set errno to indicate the error.

ERRORS

The aio_write() function shall 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 shall return -1 and set errno to the corresponding value. If any of the conditions below are detected asynchronously, the return status of the asynchronous operation shall be set to -1, and the error status of the asynchronous operation is 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, [PIO] _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 shall be one of the values normally returned by the write() 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() 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.

The following sections are informative.

EXAMPLES

None.

APPLICATION USAGE

The aio_write() function is part of the Asynchronous Input and Output option and need not be available on all implementations.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

aio_cancel(), aio_error(), aio_read(), aio_return(), close(), exec(), exit(), fork(), lio_listio(), lseek(), write(), the Base Definitions volume of IEEE Std 1003.1-2001, <aio.h>

CHANGE HISTORY

First released in Issue 5. Included for alignment with the POSIX Realtime Extension.

Large File Summit extensions are added.

Issue 6

The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the Asynchronous Input and Output option.

The APPLICATION USAGE section is added.

The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:

• In the DESCRIPTION, text is added to indicate that for regular files no data transfer occurs past the offset maximum established in the open file description associated with _aiocbp_->aio_fildes.
• The [EFBIG] error is added as part of the large file support extensions.

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/14 is applied, rewording the DESCRIPTION when prioritized I/O is supported to account for threads, and removing the words ``to the calling process'' in the RETURN VALUE section.

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/15 is applied, updating the [EINVAL] error, so that detection of an [EINVAL] error for an invalid value of _aiocbp_->aio_reqprio is only required if the Prioritized Input and Output option is supported.

End of informative text.

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