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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2003 The Open Group, All Rights Reserved --><title>lio_listio</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="lio_listio"></a> <a name="tag_03_334"></a><!-- lio_listio --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_334_01"></a>NAME</h4><blockquote>lio_listio - list directed I/O (<b>REALTIME</b>)</blockquote><h4><a name="tag_03_334_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><div class="box"><code><tt><sup>[<a href="javascript:open_code('AIO')">AIO</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> #include <<a href="../basedefs/aio.h.html">aio.h</a>><br><br> int lio_listio(int</tt> <i>mode</i><tt>, struct aiocb *restrict const</tt> <i>list</i><tt>[restrict],<br> int</tt> <i>nent</i><tt>, struct sigevent *restrict</tt> <i>sig</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div><tt><br></tt></blockquote><h4><a name="tag_03_334_03"></a>DESCRIPTION</h4><blockquote><p>The <i>lio_listio</i>() function shall initiate a list of I/O requests with a single function call.</p><p>The <i>mode</i> argument takes one of the values LIO_WAIT or LIO_NOWAIT declared in <a href="../basedefs/aio.h.html"><i><aio.h></i></a> and determines whether the function returns when the I/O operations have beencompleted, or as soon as the operations have been queued. If the <i>mode</i> argument is LIO_WAIT, the function shall wait untilall I/O is complete and the <i>sig</i> argument shall be ignored.</p><p>If the <i>mode</i> argument is LIO_NOWAIT, the function shall return immediately, and asynchronous notification shall occur,according to the <i>sig</i> argument, when all the I/O operations complete. If <i>sig</i> is NULL, then no asynchronousnotification shall occur. If <i>sig</i> is not NULL, asynchronous notification occurs as specified in <a href="xsh_chap02_04.html#tag_02_04_01"><i>Signal Generation and Delivery</i></a> when all the requests in <i>list</i> havecompleted.</p><p>The I/O requests enumerated by <i>list</i> are submitted in an unspecified order.</p><p>The <i>list</i> argument is an array of pointers to <b>aiocb</b> structures. The array contains <i>nent</i> elements. The arraymay contain NULL elements, which shall be ignored.</p><p>The <i>aio_lio_opcode</i> field of each <b>aiocb</b> structure specifies the operation to be performed. The supported operationsare LIO_READ, LIO_WRITE, and LIO_NOP; these symbols are defined in <a href="../basedefs/aio.h.html"><i><aio.h></i></a>. TheLIO_NOP operation causes the list entry to be ignored. If the <i>aio_lio_opcode</i> element is equal to LIO_READ, then an I/Ooperation is submitted as if by a call to <a href="../functions/aio_read.html"><i>aio_read</i>()</a> with the <i>aiocbp</i> equalto the address of the <b>aiocb</b> structure. If the <i>aio_lio_opcode</i> element is equal to LIO_WRITE, then an I/O operation issubmitted as if by a call to <a href="../functions/aio_write.html"><i>aio_write</i>()</a> with the <i>aiocbp</i> equal to theaddress of the <b>aiocb</b> structure.</p><p>The <i>aio_fildes</i> member specifies the file descriptor on which the operation is to be performed.</p><p>The <i>aio_buf</i> member specifies the address of the buffer to or from which the data is transferred.</p><p>The <i>aio_nbytes</i> member specifies the number of bytes of data to be transferred.</p><p>The members of the <b>aiocb</b> structure further describe the I/O operation to be performed, in a manner identical to that ofthe corresponding <b>aiocb</b> structure when used by the <a href="../functions/aio_read.html"><i>aio_read</i>()</a> and <a href="../functions/aio_write.html"><i>aio_write</i>()</a> functions.</p><p>The <i>nent</i> argument specifies how many elements are members of the list; that is, the length of the array.</p><p>The behavior of this function is altered according to the definitions of synchronized I/O data integrity completion andsynchronized I/O file integrity completion if synchronized I/O is enabled on the file associated with <i>aio_fildes</i>.</p><p>For regular files, no data transfer shall occur past the offset maximum established in the open file description associated with<i>aiocbp</i>-><i>aio_fildes</i>.</p></blockquote><h4><a name="tag_03_334_04"></a>RETURN VALUE</h4><blockquote><p>If the <i>mode</i> argument has the value LIO_NOWAIT, the <i>lio_listio</i>() function shall return the value zero if the I/Ooperations are successfully queued; otherwise, the function shall return the value -1 and set <i>errno</i> to indicate theerror.</p><p>If the <i>mode</i> argument has the value LIO_WAIT, the <i>lio_listio</i>() function shall return the value zero when all theindicated I/O has completed successfully. Otherwise, <i>lio_listio</i>() shall return a value of -1 and set <i>errno</i> toindicate the error.</p><p>In either case, the return value only indicates the success or failure of the <i>lio_listio</i>() call itself, not the status ofthe individual I/O requests. In some cases one or more of the I/O requests contained in the list may fail. Failure of an individualrequest does not prevent completion of any other individual request. To determine the outcome of each I/O request, the applicationshall examine the error status associated with each <b>aiocb</b> control block. The error statuses so returned are identical tothose returned as the result of an <a href="../functions/aio_read.html"><i>aio_read</i>()</a> or <a href="../functions/aio_write.html"><i>aio_write</i>()</a> function.</p></blockquote><h4><a name="tag_03_334_05"></a>ERRORS</h4><blockquote><p>The <i>lio_listio</i>() function shall fail if:</p><dl compact><dt>[EAGAIN]</dt><dd>The resources necessary to queue all the I/O requests were not available. The application may check the error status for each<b>aiocb</b> to determine the individual request(s) that failed.</dd><dt>[EAGAIN]</dt><dd>The number of entries indicated by <i>nent</i> would cause the system-wide limit {AIO_MAX} to be exceeded.</dd><dt>[EINVAL]</dt><dd>The <i>mode</i> argument is not a proper value, or the value of <i>nent</i> was greater than {AIO_LISTIO_MAX}.</dd><dt>[EINTR]</dt><dd>A signal was delivered while waiting for all I/O requests to complete during an LIO_WAIT operation. Note that, since each I/Ooperation invoked by <i>lio_listio</i>() may possibly provoke a signal when it completes, this error return may be caused by thecompletion of one (or more) of the very I/O operations being awaited. Outstanding I/O requests are not canceled, and theapplication shall examine each list element to determine whether the request was initiated, canceled, or completed.</dd><dt>[EIO]</dt><dd>One or more of the individual I/O operations failed. The application may check the error status for each <b>aiocb</b> structureto determine the individual request(s) that failed.</dd></dl><p>In addition to the errors returned by the <i>lio_listio</i>() function, if the <i>lio_listio</i>() function succeeds or failswith errors of [EAGAIN], [EINTR], or [EIO], then some of the I/O specified by the list may have been initiated. If the<i>lio_listio</i>() function fails with an error code other than [EAGAIN], [EINTR], or [EIO], no operations from the list shallhave been initiated. The I/O operation indicated by each list element can encounter errors specific to the individual read or writefunction being performed. In this event, the error status for each <b>aiocb</b> control block contains the associated error code.The error codes that can be set are the same as would be set by a <a href="../functions/read.html"><i>read</i>()</a> or <a href="../functions/write.html"><i>write</i>()</a> function, with the following additional error codes possible:</p><dl compact><dt>[EAGAIN]</dt><dd>The requested I/O operation was not queued due to resource limitations.</dd><dt>[ECANCELED]</dt><dd>The requested I/O was canceled before the I/O completed due to an explicit <a href="../functions/aio_cancel.html"><i>aio_cancel</i>()</a> request.</dd><dt>[EFBIG]</dt><dd>The <i>aiocbp</i>-><i>aio_lio_opcode</i> is LIO_WRITE, the file is a regular file, <i>aiocbp</i>-><i>aio_nbytes</i> isgreater than 0, and the <i>aiocbp</i>-><i>aio_offset</i> is greater than or equal to the offset maximum in the open filedescription associated with <i>aiocbp</i>-><i>aio_fildes</i>.</dd><dt>[EINPROGRESS]</dt><dd>The requested I/O is in progress.</dd><dt>[EOVERFLOW]</dt><dd>The <i>aiocbp</i>-><i>aio_lio_opcode</i> is LIO_READ, the file is a regular file, <i>aiocbp</i>-><i>aio_nbytes</i> isgreater than 0, and the <i>aiocbp</i>-><i>aio_offset</i> is before the end-of-file and is greater than or equal to the offsetmaximum in the open file description associated with <i>aiocbp</i>-><i>aio_fildes</i>.</dd></dl></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_334_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_334_07"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_334_08"></a>RATIONALE</h4><blockquote><p>Although it may appear that there are inconsistencies in the specified circumstances for error codes, the [EIO] error conditionapplies when any circumstance relating to an individual operation makes that operation fail. This might be due to a badlyformulated request (for example, the <i>aio_lio_opcode</i> field is invalid, and <a href="../functions/aio_error.html"><i>aio_error</i>()</a> returns [EINVAL]) or might arise from application behavior (for example, thefile descriptor is closed before the operation is initiated, and <a href="../functions/aio_error.html"><i>aio_error</i>()</a>returns [EBADF]).</p><p>The limitation on the set of error codes returned when operations from the list shall have been initiated enables applicationsto know when operations have been started and whether <a href="../functions/aio_error.html"><i>aio_error</i>()</a> is valid for aspecific operation.</p></blockquote><h4><a name="tag_03_334_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_334_10"></a>SEE ALSO</h4><blockquote><p><a href="aio_read.html"><i>aio_read</i>()</a> , <a href="aio_write.html"><i>aio_write</i>()</a> , <a href="aio_error.html"><i>aio_error</i>()</a> , <a href="aio_return.html"><i>aio_return</i>()</a> , <a href="aio_cancel.html"><i>aio_cancel</i>()</a> , <a href="close.html"><i>close</i>()</a> , <a href="exec.html"><i><a href="../functions/exec.html">exec</a></i>()</a> , <a href="exit.html"><i>exit</i>()</a> , <a href="fork.html"><i>fork</i>()</a> , <ahref="lseek.html"><i>lseek</i>()</a> , <a href="read.html"><i>read</i>()</a> , the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/aio.h.html"><i><aio.h></i></a></p></blockquote><h4><a name="tag_03_334_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 5. Included for alignment with the POSIX Realtime Extension.</p><p>Large File Summit extensions are added.</p></blockquote><h4><a name="tag_03_334_12"></a>Issue 6</h4><blockquote><p>The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support theAsynchronous Input and Output option.</p><p>The <i>lio_listio</i>() function is marked as part of the Asynchronous Input and Output option.</p><p>The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:</p><ul><li><p>In the DESCRIPTION, text is added to indicate that for regular files no data transfer occurs past the offset maximum establishedin the open file description associated with <i>aiocbp</i>-><i>aio_fildes</i>. This change is to support large files.</p></li><li><p>The [EBIG] and [EOVERFLOW] error conditions are defined. This change is to support large files.</p></li></ul><p>The DESCRIPTION is updated to avoid use of the term "must" for application requirements.</p><p>The <b>restrict</b> keyword is added to the <i>lio_listio</i>() prototype for alignment with the ISO/IEC 9899:1999standard.</p></blockquote><div class="box"><em>End of informative text.</em></div><hr><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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