FreeBSD Manual Pages
AIO_WRITE(2) BSD 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 The aio_write() system call allows the calling process to write iocb-_aio_nbytes from the buffer pointed to by iocb-_aio_buf to the de- scriptor 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 abso- lute 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 en- queued 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 the aio_write() system call to avoid passing bogus context information to the kernel. Modifications of the Asynchronous I/O Control Block structure or the buf- fer 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 The aio_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 The aio_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. The following conditions may be synchronously detected when the aio_write() system call is made, or asynchronously, at any time there- after. 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 prior- ity, or the number of bytes specified by iocb-_aio_nbytes is not valid. If the request is successfully enqueued, but subsequently canceled or an error occurs, the value returned by the aio_return() system call is per the write(2) system call, and the value returned by the aio_error() sys- tem 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 The aio_write() system call is expected to conform to the IEEE Std 1003.1 ("POSIX.1") standard. HISTORY The aio_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. BSD June 2, 1999 BSD
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RESTRICTIONS | RETURN VALUES | ERRORS | SEE ALSO | STANDARDS | HISTORY | AUTHORS | BUGS
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=aio_write&sektion=2&manpath=FreeBSD+9.1-RELEASE>