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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.
89 The Asynchronous I/O Control Block structure pointed to by
91 and the buffer that the
93 member of that structure references must remain valid until the
94 operation has completed.
95 For this reason, use of auto (stack) variables
96 for these objects is discouraged.
98 The asynchronous I/O control buffer
100 should be zeroed before the
102 system call to avoid passing bogus context information to the kernel.
104 Modifications of the Asynchronous I/O Control Block structure or the
105 buffer contents after the request has been enqueued, but before the
106 request has completed, are not allowed.
108 If the file offset in
110 is past the offset maximum for
111 .Fa iocb->aio_fildes ,
118 system call will fail if:
121 The request was not queued because of system resource limitations.
125 system call is not supported.
128 The following conditions may be synchronously detected when the
130 system call is made, or asynchronously, at any time thereafter.
132 are detected at call time,
136 appropriately; otherwise the
138 system call must be called, and will return -1, and
140 must be called to determine the actual value that would have been
148 is invalid, or is not opened for writing.
152 is not valid, the priority specified by
153 .Fa iocb->aio_reqprio
154 is not a valid priority, or the number of bytes specified by
159 If the request is successfully enqueued, but subsequently canceled
160 or an error occurs, the value returned by the
162 system call is per the
164 system call, and the value returned by the
166 system call is either one of the error returns from the
168 system call, or one of:
174 is invalid for writing.
176 The request was explicitly canceled via a call to
188 .Xr aio_waitcomplete 2 ,
195 is expected to conform to the
201 system call first appeared in
204 This manual page was written by
205 .An Wes Peters Aq wes@softweyr.com .
207 Invalid information in
208 .Fa iocb->_aiocb_private
209 may confuse the kernel.