NAME

aio_write − asynchronous write

SYNOPSIS

#include <aio.h>

int aio_write(aiocbp)

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 after the request is successfully queued. 

If O_APPEND is not set for the file descriptor aiocbp->aio_fildes, then the write operation takes place at the absolute position in the file as given by aiocbp->aio_offset, as if lseek(2) were called immediately prior to the operation with an offset equal to aiocbp->aio_offset, and a whence equal to SEEK_SET. If O_APPEND is set for the file descriptor, the write operation is appended to the end of the file.  After a successful call to queue an asynchronous write operation, the value of the file offset for the file is aiocbp->aio_offset plus aiocbp->aionbytes. 

If prioritized I/O is supported for the specified file and the process is scheduled under either the SCHED_RR or SCHED_FIFO scheduling policies, then the asynchronous write operation is submitted at a priority equal to (process priority minus aiocbp->aio_reqprio).  aiocbp->aio_reqprio must be a value from zero through AIO_PRIO_DELTA_MAX.  Currently, prioritized I/O is only supported for disk files. 

The aiocbp->aio_lio_opcode field is ignored by aio_write. 

If synchronized I/O is enabled on the file associated with aiocbp->aio_fildes, the behavior of this function is modified according to the definitions of synchronized I/O data integrity completion and synchronized I/O file integrity completion.  See open(2) and fcntl(2). 

On close(2), cancelable operations for the file descriptor may be deleted. All operations which are not canceled are completed as if the close(2) blocked until the operations completed.  An asynchronous I/O request is still cancelable if the request hasn’t been submitted to the device. 

On _exit(2) and exec(2), cancelable operations for all file descriptors may be deleted. All operations which are not canceled shall complete as if there were no calls to _exit(2) or exec(2), but any associated signal notifications are suppressed. For fork(2), no asynchronous I/O is inherited. 

RETURN VALUE

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

If any of the following conditions occur, the aio_write function returns a -1 and sets errno to the corresponding value:

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

[EFAULT] The system is unable to access the aiocb structure that the aiocbp argument points to. 

[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. 

If the aio_write call successfully queues the I/O operation but the operation is subsequently canceled or encounters an error, the error status of the asynchronous operation, which is returned by aio_error(3P4) will be one of the errors normally returned by the write(2) function call.  If the operation is canceled via the aio_cancel(3P4) function, the status of the asynchronous operation will be ECANCELED.

FILES

/usr/lib/libposix4.a

SEE ALSO

aio_read(3P4), aio_fsync(3P4), aio_error(3P4), aio_return(3P4), aio_cancel(3P4), aio_suspend(3P4), lio_listio(3P4), "CX/UX Programmer’s Guide"

WARNING

The interface to aio_write is based on IEEE Draft Standard P1003.4/D12.  This is an unapproved draft, subject to change.  Use of information contained in this unapproved draft is at your own risk.  This interface will change to reflect any changes made by future drafts of POSIX 1003.4. 
 

CX/UX Programmer’s Reference Manual