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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>posix_fadvise</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="posix_fadvise"></a> <a name="tag_03_421"></a><!-- posix_fadvise --> <!--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_421_01"></a>NAME</h4><blockquote>posix_fadvise - file advisory information (<b>ADVANCED REALTIME</b>)</blockquote><h4><a name="tag_03_421_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><div class="box"><code><tt><sup>[<a href="javascript:open_code('ADV')">ADV</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> #include <<a href="../basedefs/fcntl.h.html">fcntl.h</a>><br><br> int posix_fadvise(int</tt> <i>fd</i><tt>, off_t</tt> <i>offset</i><tt>, size_t</tt> <i>len</i><tt>, int</tt> <i>advice</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_421_03"></a>DESCRIPTION</h4><blockquote><p>The <i>posix_fadvise</i>() function shall advise the implementation on the expected behavior of the application with respect tothe data in the file associated with the open file descriptor, <i>fd</i>, starting at <i>offset</i> and continuing for <i>len</i>bytes. The specified range need not currently exist in the file. If <i>len</i> is zero, all data following <i>offset</i> isspecified. The implementation may use this information to optimize handling of the specified data. The <i>posix_fadvise</i>()function shall have no effect on the semantics of other operations on the specified data, although it may affect the performance ofother operations.</p><p>The advice to be applied to the data is specified by the <i>advice</i> parameter and may be one of the following values:</p><dl compact><dt>POSIX_FADV_NORMAL</dt><dd><br>Specifies that the application has no advice to give on its behavior with respect to the specified data. It is the defaultcharacteristic if no advice is given for an open file.</dd><dt>POSIX_FADV_SEQUENTIAL</dt><dd><br>Specifies that the application expects to access the specified data sequentially from lower offsets to higher offsets.</dd><dt>POSIX_FADV_RANDOM</dt><dd><br>Specifies that the application expects to access the specified data in a random order.</dd><dt>POSIX_FADV_WILLNEED</dt><dd><br>Specifies that the application expects to access the specified data in the near future.</dd><dt>POSIX_FADV_DONTNEED</dt><dd><br>Specifies that the application expects that it will not access the specified data in the near future.</dd><dt>POSIX_FADV_NOREUSE</dt><dd><br>Specifies that the application expects to access the specified data once and then not reuse it thereafter.</dd></dl><p>These values are defined in <a href="../basedefs/fcntl.h.html"><i><fcntl.h></i></a>.</p></blockquote><h4><a name="tag_03_421_04"></a>RETURN VALUE</h4><blockquote><p>Upon successful completion, <i>posix_fadvise</i>() shall return zero; otherwise, an error number shall be returned to indicatethe error.</p></blockquote><h4><a name="tag_03_421_05"></a>ERRORS</h4><blockquote><p>The <i>posix_fadvise</i>() function shall fail if:</p><dl compact><dt>[EBADF]</dt><dd>The <i>fd</i> argument is not a valid file descriptor.</dd><dt>[EINVAL]</dt><dd>The value of <i>advice</i> is invalid.</dd><dt>[ESPIPE]</dt><dd>The <i>fd</i> argument is associated with a pipe or FIFO.</dd></dl></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_421_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_421_07"></a>APPLICATION USAGE</h4><blockquote><p>The <i>posix_fadvise</i>() function is part of the Advisory Information option and need not be provided on allimplementations.</p></blockquote><h4><a name="tag_03_421_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_421_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_421_10"></a>SEE ALSO</h4><blockquote><p><a href="posix_madvise.html"><i>posix_madvise</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <ahref="../basedefs/fcntl.h.html"><i><fcntl.h></i></a></p></blockquote><h4><a name="tag_03_421_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 6. Derived from IEEE Std 1003.1d-1999.</p><p>In the SYNOPSIS, the inclusion of <a href="../basedefs/sys/types.h.html"><i><sys/types.h></i></a> is no longerrequired.</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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