230 lines
9.9 KiB
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230 lines
9.9 KiB
HTML
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<title>aio_write</title>
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<basefont size="3"> <a name="aio_write"></a> <a name="tag_03_20"></a><!-- aio_write -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_20_01"></a>NAME</h4>
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<blockquote>aio_write - asynchronous write to a file (<b>REALTIME</b>)</blockquote>
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<h4><a name="tag_03_20_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('AIO')">AIO</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <<a href="../basedefs/aio.h.html">aio.h</a>><br>
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<br>
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int aio_write(struct aiocb *</tt><i>aiocbp</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_20_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>aio_write</i>() function shall write <i>aiocbp</i>-><i>aio_nbytes</i> to the file associated with
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<i>aiocbp</i>-><i>aio_fildes</i> from the buffer pointed to by <i>aiocbp</i>-><i>aio_buf</i>. The function shall return when
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the write request has been initiated or, at a minimum, queued to the file or device.</p>
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<p><sup>[<a href="javascript:open_code('PIO')">PIO</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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If prioritized I/O is supported for this file, then the asynchronous operation shall be submitted at a priority equal to the
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scheduling priority of the process minus <i>aiocbp</i>-><i>aio_reqprio</i>. <img src="../images/opt-end.gif" alt="[Option End]"
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border="0"></p>
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<p>The <i>aiocbp</i> argument may be used as an argument to <a href="../functions/aio_error.html"><i>aio_error</i>()</a> and <a
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href="../functions/aio_return.html"><i>aio_return</i>()</a> in order to determine the error status and return status, respectively,
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of the asynchronous operation while it is proceeding.</p>
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<p>The <i>aiocbp</i> argument points to an <b>aiocb</b> structure. If the buffer pointed to by <i>aiocbp</i>-><i>aio_buf</i> or
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the control block pointed to by <i>aiocbp</i> becomes an illegal address prior to asynchronous I/O completion, then the behavior is
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undefined.</p>
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<p>If O_APPEND is not set for the file descriptor <i>aio_fildes</i>, then the requested operation shall take place at the absolute
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position in the file as given by <i>aio_offset</i>, as if <a href="../functions/lseek.html"><i>lseek</i>()</a> were called
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immediately prior to the operation with an <i>offset</i> equal to <i>aio_offset</i> and a <i>whence</i> equal to SEEK_SET. If
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O_APPEND is set for the file descriptor, write operations append to the file in the same order as the calls were made. After a
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successful call to enqueue an asynchronous I/O operation, the value of the file offset for the file is unspecified.</p>
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<p>The <i>aiocbp</i>-><i>aio_lio_opcode</i> field shall be ignored by <i>aio_write</i>().</p>
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<p>Simultaneous asynchronous operations using the same <i>aiocbp</i> produce undefined results.</p>
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<p><sup>[<a href="javascript:open_code('SIO')">SIO</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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If synchronized I/O is enabled on the file associated with <i>aiocbp</i>-><i>aio_fildes</i>, the behavior of this function shall
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be according to the definitions of synchronized I/O data integrity completion, and synchronized I/O file integrity completion. <img
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src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
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<p>For any system action that changes the process memory space while an asynchronous I/O is outstanding to the address range being
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changed, the result of that action is undefined.</p>
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<p>For regular files, no data transfer shall occur past the offset maximum established in the open file description associated with
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<i>aiocbp</i>-><i>aio_fildes</i>.</p>
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</blockquote>
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<h4><a name="tag_03_20_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>The <i>aio_write</i>() function shall return the value zero to the calling process if the I/O operation is successfully queued;
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otherwise, the function shall return the value -1 and set <i>errno</i> to indicate the error.</p>
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</blockquote>
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<h4><a name="tag_03_20_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>aio_write</i>() function shall fail if:</p>
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<dl compact>
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<dt>[EAGAIN]</dt>
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<dd>The requested asynchronous I/O operation was not queued due to system resource limitations.</dd>
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</dl>
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<p>Each of the following conditions may be detected synchronously at the time of the call to <i>aio_write</i>(), or asynchronously.
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If any of the conditions below are detected synchronously, the <i>aio_write</i>() function shall return -1 and set <i>errno</i> to
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the corresponding value. If any of the conditions below are detected asynchronously, the return status of the asynchronous
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operation shall be set to -1, and the error status of the asynchronous operation is set to the corresponding value.</p>
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<dl compact>
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<dt>[EBADF]</dt>
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<dd>The <i>aiocbp</i>-><i>aio_fildes</i> argument is not a valid file descriptor open for writing.</dd>
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<dt>[EINVAL]</dt>
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<dd>The file offset value implied by <i>aiocbp</i>-><i>aio_offset</i> would be invalid, <i>aiocbp</i>-><i>aio_reqprio</i> is
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not a valid value, or <i>aiocbp</i>-><i>aio_nbytes</i> is an invalid value.</dd>
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</dl>
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<p>In the case that the <i>aio_write</i>() successfully queues the I/O operation, the return status of the asynchronous operation
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shall be one of the values normally returned by the <a href="../functions/write.html"><i>write</i>()</a> function call. If the
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operation is successfully queued but is subsequently canceled or encounters an error, the error status for the asynchronous
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operation contains one of the values normally set by the <a href="../functions/write.html"><i>write</i>()</a> function call, or one
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of the following:</p>
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<dl compact>
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<dt>[EBADF]</dt>
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<dd>The <i>aiocbp</i>-><i>aio_fildes</i> argument is not a valid file descriptor open for writing.</dd>
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<dt>[EINVAL]</dt>
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<dd>The file offset value implied by <i>aiocbp</i>-><i>aio_offset</i> would be invalid.</dd>
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<dt>[ECANCELED]</dt>
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<dd>The requested I/O was canceled before the I/O completed due to an explicit <a href=
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"../functions/aio_cancel.html"><i>aio_cancel</i>()</a> request.</dd>
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</dl>
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<p>The following condition may be detected synchronously or asynchronously:</p>
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<dl compact>
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<dt>[EFBIG]</dt>
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<dd>The file is a regular file, <i>aiobcp</i>-><i>aio_nbytes</i> is greater than 0, and the starting offset in
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<i>aiobcp</i>-><i>aio_offset</i> is at or beyond the offset maximum in the open file description associated with
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<i>aiocbp</i>-><i>aio_fildes</i>.</dd>
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</dl>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_20_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_20_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>The <i>aio_write</i>() function is part of the Asynchronous Input and Output option and need not be available on all
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implementations.</p>
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</blockquote>
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<h4><a name="tag_03_20_08"></a>RATIONALE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_20_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_20_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="aio_cancel.html"><i>aio_cancel</i>()</a> , <a href="aio_error.html"><i>aio_error</i>()</a> , <a href=
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"aio_read.html"><i>aio_read</i>()</a> , <a href="aio_return.html"><i>aio_return</i>()</a> , <a href="close.html"><i>close</i>()</a>
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, <a href="exec.html"><i><a href="../functions/exec.html">exec</a></i>()</a> , <a href="exit.html"><i>exit</i>()</a> , <a href=
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"fork.html"><i>fork</i>()</a> , <a href="lio_listio.html"><i>lio_listio</i>()</a> , <a href="lseek.html"><i>lseek</i>()</a> , <a
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href="write.html"><i>write</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/aio.h.html"><i><aio.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_20_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 5. Included for alignment with the POSIX Realtime Extension.</p>
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<p>Large File Summit extensions are added.</p>
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</blockquote>
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<h4><a name="tag_03_20_12"></a>Issue 6</h4>
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<blockquote>
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<p>The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the
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Asynchronous Input and Output option.</p>
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<p>The APPLICATION USAGE section is added.</p>
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<p>The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:</p>
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<ul>
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<li>
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<p>In the DESCRIPTION, text is added to indicate that for regular files no data transfer occurs past the offset maximum established
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in the open file description associated with <i>aiocbp</i>-><i>aio_fildes</i>.</p>
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</li>
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<li>
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<p>The [EFBIG] error is added as part of the large file support extensions.</p>
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</li>
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</ul>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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<hr>
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