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32 .Nd asynchronous write to a file (REALTIME)
38 .Fn aio_write "struct aiocb *iocb"
42 system call allows the calling process to write
44 from the buffer pointed to by
47 .Fa iocb->aio_fildes .
48 The call returns immediately after the write request has been enqueued
49 to the descriptor; the write may or may not have completed at the time
51 If the request could not be enqueued, generally due
52 to invalid arguments, the call returns without having enqueued the
58 .Fa iocb->aio_fildes ,
60 operations append to the file in the same order as the calls were
64 is not set for the file descriptor, the write operation will occur at
65 the absolute position from the beginning of the file plus
66 .Fa iocb->aio_offset .
69 .Dv _POSIX_PRIORITIZED_IO
70 is defined, and the descriptor supports it, then the enqueued
71 operation is submitted at a priority equal to that of the calling
73 .Fa iocb->aio_reqprio .
77 pointer may be subsequently used as an argument to
81 in order to determine return or error status for the enqueued operation
82 while it is in progress.
84 If the request is successfully enqueued, the value of
86 can be modified during the request as context, so this value must not
87 be referenced after the request is enqueued.
90 .Fa iocb->aio_sigevent
91 structure can be used to request notification of the operation's
92 completion as described in
95 The Asynchronous I/O Control Block structure pointed to by
97 and the buffer that the
99 member of that structure references must remain valid until the
100 operation has completed.
102 The asynchronous I/O control buffer
104 should be zeroed before the
106 system call to avoid passing bogus context information to the kernel.
108 Modifications of the Asynchronous I/O Control Block structure or the
109 buffer contents are not allowed while the request is queued.
111 If the file offset in
113 is past the offset maximum for
114 .Fa iocb->aio_fildes ,
121 system call will fail if:
124 The request was not queued because of system resource limitations.
126 The asynchronous notification method in
127 .Fa iocb->aio_sigevent.sigev_notify
128 is invalid or not supported.
130 Asynchronous write operations on the file descriptor
132 are unsafe and unsafe asynchronous I/O operations are disabled.
135 The following conditions may be synchronously detected when the
137 system call is made, or asynchronously, at any time thereafter.
139 are detected at call time,
143 appropriately; otherwise the
145 system call must be called, and will return -1, and
147 must be called to determine the actual value that would have been
155 is invalid, or is not opened for writing.
159 is not valid, the priority specified by
160 .Fa iocb->aio_reqprio
161 is not a valid priority, or the number of bytes specified by
166 If the request is successfully enqueued, but subsequently canceled
167 or an error occurs, the value returned by the
169 system call is per the
171 system call, and the value returned by the
173 system call is either one of the error returns from the
175 system call, or one of:
181 is invalid for writing.
183 The request was explicitly canceled via a call to
195 .Xr aio_waitcomplete 2 ,
203 is expected to conform to the
209 system call first appeared in
212 This manual page was written by
213 .An Wes Peters Aq Mt wes@softweyr.com .
215 Invalid information in
216 .Fa iocb->_aiocb_private
217 may confuse the kernel.