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31 .Nd asynchronous write to a file (REALTIME)
37 .Fn aio_write "struct aiocb *iocb"
40 .Fn aio_writev "struct aiocb *iocb"
46 system calls allow the calling process to write
48 .Fa iocb->aio_fildes .
52 from the buffer pointed to by
56 gathers the data from the
58 buffers specified by the members of the
61 Both syscalls return immediately after the write request has been enqueued
62 to the descriptor; the write may or may not have completed at the time
64 If the request could not be enqueued, generally due
65 to invalid arguments, the call returns without having enqueued the
72 structure is defined in
78 .Fa iocb->aio_fildes ,
79 write operations append to the file in the same order as the calls were
83 is not set for the file descriptor, the write operation will occur at
84 the absolute position from the beginning of the file plus
85 .Fa iocb->aio_offset .
89 pointer may be subsequently used as an argument to
93 in order to determine return or error status for the enqueued operation
94 while it is in progress.
96 If the request is successfully enqueued, the value of
98 can be modified during the request as context, so this value must not
99 be referenced after the request is enqueued.
102 .Fa iocb->aio_sigevent
103 structure can be used to request notification of the operation's
104 completion as described in
107 The Asynchronous I/O Control Block structure pointed to by
109 and the buffer that the
111 member of that structure references must remain valid until the
112 operation has completed.
114 The asynchronous I/O control buffer
116 should be zeroed before the
120 system call to avoid passing bogus context information to the kernel.
122 Modifications of the Asynchronous I/O Control Block structure or the
123 buffer contents are not allowed while the request is queued.
125 If the file offset in
127 is past the offset maximum for
128 .Fa iocb->aio_fildes ,
131 .Rv -std aio_write aio_writev
137 system calls will fail if:
140 The request was not queued because of system resource limitations.
144 points outside the process's allocated address space.
146 The asynchronous notification method in
147 .Fa iocb->aio_sigevent.sigev_notify
148 is invalid or not supported.
150 Asynchronous write operations on the file descriptor
152 are unsafe and unsafe asynchronous I/O operations are disabled.
155 The following conditions may be synchronously detected when the
159 system call is made, or asynchronously, at any time thereafter.
161 are detected at call time,
167 appropriately; otherwise the
169 system call must be called, and will return -1, and
171 must be called to determine the actual value that would have been
179 is invalid, or is not opened for writing.
183 is not valid, the priority specified by
184 .Fa iocb->aio_reqprio
185 is not a valid priority, or the number of bytes specified by
190 If the request is successfully enqueued, but subsequently canceled
191 or an error occurs, the value returned by the
193 system call is per the
195 system call, and the value returned by the
197 system call is either one of the error returns from the
199 system call, or one of:
205 is invalid for writing.
207 The request was explicitly canceled via a call to
219 .Xr aio_waitcomplete 2 ,
227 is expected to conform to the
233 system call is a FreeBSD extension, and should not be used in portable code.
237 system call first appeared in
241 system call first appeared in
244 This manual page was written by
245 .An Wes Peters Aq Mt wes@softweyr.com .
247 Invalid information in
248 .Fa iocb->_aiocb_private
249 may confuse the kernel.