.\" Copyright (c) 2003 Andries Brouwer (aeb@cwi.nl)
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.TH AIO_WRITE 3 2021-03-22  "" "Linux Programmer's Manual"
.SH NAME
aio_write \- asynchronous write
.SH SYNOPSIS
.nf
.B "#include <aio.h>"
.PP
.BI "int aio_write(struct aiocb *" aiocbp );
.PP
Link with \fI\-lrt\fP.
.fi
.SH DESCRIPTION
The
.BR aio_write ()
function queues the I/O request described by the buffer pointed to by
.IR aiocbp .
This function is the asynchronous analog of
.BR write (2).
The arguments of the call
.PP
    write(fd, buf, count)
.PP
correspond (in order) to the fields
.IR aio_fildes ,
.IR aio_buf ,
and
.IR aio_nbytes
of the structure pointed to by
.IR aiocbp .
(See
.BR aio (7)
for a description of the
.I aiocb
structure.)
.PP
If
.B O_APPEND
is not set, the data is written starting at the
absolute position
.IR aiocbp\->aio_offset ,
regardless of the file offset.
If
.B O_APPEND
is set, data is written at the end of the file in the same order as
.BR aio_write ()
calls are made.
After the call, the value of the file offset is unspecified.
.PP
The "asynchronous" means that this call returns as soon as the
request has been enqueued; the write may or may not have completed
when the call returns.
One tests for completion using
.BR aio_error (3).
The return status of a completed I/O operation can be obtained
.BR aio_return (3).
Asynchronous notification of I/O completion can be obtained by setting
.IR aiocbp\->aio_sigevent
appropriately; see
.BR sigevent (7)
for details.
.PP
If
.B _POSIX_PRIORITIZED_IO
is defined, and this file supports it,
then the asynchronous operation is submitted at a priority equal
to that of the calling process minus
.IR aiocbp\->aio_reqprio .
.PP
The field
.I aiocbp\->aio_lio_opcode
is ignored.
.PP
No data is written to a regular file beyond its maximum offset.
.SH RETURN VALUE
On success, 0 is returned.
On error, the request is not enqueued, \-1
is returned, and
.I errno
is set to indicate the error.
If an error is detected only later, it will
be reported via
.BR aio_return (3)
(returns status \-1) and
.BR aio_error (3)
(error status\(emwhatever one would have gotten in
.IR errno ,
such as
.BR EBADF ).
.SH ERRORS
.TP
.B EAGAIN
Out of resources.
.TP
.B EBADF
.I aio_fildes
is not a valid file descriptor open for writing.
.TP
.B EFBIG
The file is a regular file, we want to write at least one byte,
but the starting position is at or beyond the maximum offset for this file.
.TP
.B EINVAL
One or more of
.IR aio_offset ,
.IR aio_reqprio ,
.I aio_nbytes
are invalid.
.TP
.B ENOSYS
.BR aio_write ()
is not implemented.
.SH VERSIONS
The
.BR aio_write ()
function is available since glibc 2.1.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.BR aio_write ()
T}	Thread safety	MT-Safe
.TE
.hy
.ad
.sp 1
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
.SH NOTES
It is a good idea to zero out the control block before use.
The control block must not be changed while the write operation
is in progress.
The buffer area being written out
.\" or the control block of the operation
must not be accessed during the operation or undefined results may occur.
The memory areas involved must remain valid.
.PP
Simultaneous I/O operations specifying the same
.I aiocb
structure produce undefined results.
.SH SEE ALSO
.BR aio_cancel (3),
.BR aio_error (3),
.BR aio_fsync (3),
.BR aio_read (3),
.BR aio_return (3),
.BR aio_suspend (3),
.BR lio_listio (3),
.BR aio (7)