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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 request'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.
101 For this reason, use of auto (stack) variables
102 for these objects is discouraged.
104 The asynchronous I/O control buffer
106 should be zeroed before the
108 system call to avoid passing bogus context information to the kernel.
110 Modifications of the Asynchronous I/O Control Block structure or the
111 buffer contents after the request has been enqueued, but before the
112 request has completed, are not allowed.
114 If the file offset in
116 is past the offset maximum for
117 .Fa iocb->aio_fildes ,
124 system call will fail if:
127 The request was not queued because of system resource limitations.
129 The asynchronous notification method in
130 .Fa iocb->aio_sigevent.sigev_notify
131 is invalid or not supported.
135 system call is not supported.
138 The following conditions may be synchronously detected when the
140 system call is made, or asynchronously, at any time thereafter.
142 are detected at call time,
146 appropriately; otherwise the
148 system call must be called, and will return -1, and
150 must be called to determine the actual value that would have been
158 is invalid, or is not opened for writing.
162 is not valid, the priority specified by
163 .Fa iocb->aio_reqprio
164 is not a valid priority, or the number of bytes specified by
169 If the request is successfully enqueued, but subsequently canceled
170 or an error occurs, the value returned by the
172 system call is per the
174 system call, and the value returned by the
176 system call is either one of the error returns from the
178 system call, or one of:
184 is invalid for writing.
186 The request was explicitly canceled via a call to
198 .Xr aio_waitcomplete 2 ,
206 is expected to conform to the
212 system call first appeared in
215 This manual page was written by
216 .An Wes Peters Aq wes@softweyr.com .
218 Invalid information in
219 .Fa iocb->_aiocb_private
220 may confuse the kernel.