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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><fcntl.h></title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="<fcntl.h>"></a> <a name="tag_13_11"></a><!-- <fcntl.h> --> <!--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_13_11_01"></a>NAME</h4><blockquote>fcntl.h - file control options</blockquote><h4><a name="tag_13_11_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><tt>#include <fcntl.h></tt></p></blockquote><h4><a name="tag_13_11_03"></a>DESCRIPTION</h4><blockquote><p>The <i><fcntl.h></i> header shall define the following requests and arguments for use by the functions <a href="../functions/fcntl.html"><i>fcntl</i>()</a> and <a href="../functions/open.html"><i>open</i>()</a>.</p><p>Values for <i>cmd</i> used by <a href="../functions/fcntl.html"><i>fcntl</i>()</a> (the following values are unique) are asfollows:</p><dl compact><dt>F_DUPFD</dt><dd>Duplicate file descriptor.</dd><dt>F_GETFD</dt><dd>Get file descriptor flags.</dd><dt>F_SETFD</dt><dd>Set file descriptor flags.</dd><dt>F_GETFL</dt><dd>Get file status flags and file access modes.</dd><dt>F_SETFL</dt><dd>Set file status flags.</dd><dt>F_GETLK</dt><dd>Get record locking information.</dd><dt>F_SETLK</dt><dd>Set record locking information.</dd><dt>F_SETLKW</dt><dd>Set record locking information; wait if blocked.</dd><dt>F_GETOWN</dt><dd>Get process or process group ID to receive SIGURG signals.</dd><dt>F_SETOWN</dt><dd>Set process or process group ID to receive SIGURG signals.</dd></dl><p>File descriptor flags used for <a href="../functions/fcntl.html"><i>fcntl</i>()</a> are as follows:</p><dl compact><dt>FD_CLOEXEC</dt><dd>Close the file descriptor upon execution of an <i>exec</i> family function.</dd></dl><p>Values for <i>l_type</i> used for record locking with <a href="../functions/fcntl.html"><i>fcntl</i>()</a> (the following valuesare unique) are as follows:</p><dl compact><dt>F_RDLCK</dt><dd>Shared or read lock.</dd><dt>F_UNLCK</dt><dd>Unlock.</dd><dt>F_WRLCK</dt><dd>Exclusive or write lock.</dd></dl><p><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">The values used for <i>l_whence</i>, SEEK_SET, SEEK_CUR, and SEEK_END shall be defined as described in <a href="unistd.h.html"><i><unistd.h></i></a> . <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p><p>The following values are file creation flags and are used in the <i>oflag</i> value to <a href="../functions/open.html"><i>open</i>()</a>. They shall be bitwise-distinct.</p><dl compact><dt>O_CREAT</dt><dd>Create file if it does not exist.</dd><dt>O_EXCL</dt><dd>Exclusive use flag.</dd><dt>O_NOCTTY</dt><dd>Do not assign controlling terminal.</dd><dt>O_TRUNC</dt><dd>Truncate flag.</dd></dl><p>File status flags used for <a href="../functions/open.html"><i>open</i>()</a> and <a href="../functions/fcntl.html"><i>fcntl</i>()</a> are as follows:</p><dl compact><dt>O_APPEND</dt><dd>Set append mode.</dd><dt>O_DSYNC</dt><dd><sup>[<a href="javascript:open_code('SIO')">SIO</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Write according to synchronized I/O data integrity completion. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd><dt>O_NONBLOCK</dt><dd>Non-blocking mode.</dd><dt>O_RSYNC</dt><dd><sup>[<a href="javascript:open_code('SIO')">SIO</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Synchronized read I/O operations. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd><dt>O_SYNC</dt><dd>Write according to synchronized I/O file integrity completion.</dd></dl><p>Mask for use with file access modes is as follows:</p><dl compact><dt>O_ACCMODE</dt><dd>Mask for file access modes.</dd></dl><p>File access modes used for <a href="../functions/open.html"><i>open</i>()</a> and <a href="../functions/fcntl.html"><i>fcntl</i>()</a> are as follows:</p><dl compact><dt>O_RDONLY</dt><dd>Open for reading only.</dd><dt>O_RDWR</dt><dd>Open for reading and writing.</dd><dt>O_WRONLY</dt><dd>Open for writing only.</dd></dl><p><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">The symbolic names for file modes for use as values of <b>mode_t</b> shall be defined as described in <a href="sys/stat.h.html"><i><sys/stat.h></i></a> . <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p><p><sup>[<a href="javascript:open_code('ADV')">ADV</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Values for <i>advice</i> used by <a href="../functions/posix_fadvise.html"><i>posix_fadvise</i>()</a> are as follows:</p><dl compact><dt>POSIX_FADV_NORMAL</dt><dd><br>The application has no advice to give on its behavior with respect to the specified data. It is the default characteristic if noadvice is given for an open file.</dd><dt>POSIX_FADV_SEQUENTIAL</dt><dd><br>The application expects to access the specified data sequentially from lower offsets to higher offsets.</dd><dt>POSIX_FADV_RANDOM</dt><dd><br>The application expects to access the specified data in a random order.</dd><dt>POSIX_FADV_WILLNEED</dt><dd><br>The application expects to access the specified data in the near future.</dd><dt>POSIX_FADV_DONTNEED</dt><dd><br>The application expects that it will not access the specified data in the near future.</dd><dt>POSIX_FADV_NOREUSE</dt><dd><br>The application expects to access the specified data once and then not reuse it thereafter.</dd></dl><img src="../images/opt-end.gif" alt="[Option End]" border="0"> <p>The structure <b>flock</b> describes a file lock. It shall include the following members:</p><pre><tt>short l_type </tt> Type of lock; F_RDLCK, F_WRLCK, F_UNLCK. <tt>short l_whence</tt> Flag for starting offset. <tt>off_t l_start </tt> Relative offset in bytes. <tt>off_t l_len </tt> Size; if 0 then until EOF. <tt>pid_t l_pid </tt> Process ID of the process holding the lock; returned with F_GETLK. <tt></tt></pre><p>The <b>mode_t</b>, <b>off_t</b>, and <b>pid_t</b> types shall be defined as described in <a href="sys/types.h.html"><i><sys/types.h></i></a> .</p><p>The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.</p><pre><tt>int creat(const char *, mode_t);int fcntl(int, int, ...);int open(const char *, int, ...);<sup>[<a href="javascript:open_code('ADV')">ADV</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">int posix_fadvise(int, off_t, size_t, int);int posix_fallocate(int, off_t, size_t);<img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></pre><p><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Inclusion of the <i><fcntl.h></i> header may also make visible all symbols from <a href="../basedefs/sys/stat.h.html"><i><sys/stat.h></i></a> and <a href="../basedefs/unistd.h.html"><i><unistd.h></i></a>.<img src="../images/opt-end.gif" alt="[Option End]" border="0"></p></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_13_11_04"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_13_11_05"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_13_11_06"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_13_11_07"></a>SEE ALSO</h4><blockquote><p><a href="sys/stat.h.html"><i><sys/stat.h></i></a> , <a href="sys/types.h.html"><i><sys/types.h></i></a> , <a href="unistd.h.html"><i><unistd.h></i></a> , the System Interfaces volume of IEEE Std 1003.1-2001, <a href="../functions/creat.html"><i>creat</i>()</a>, <i>exec</i>, <a href="../functions/fcntl.html"><i>fcntl</i>()</a>, <a href="../functions/open.html"><i>open</i>()</a>, <a href="../functions/posix_fadvise.html"><i>posix_fadvise</i>()</a>, <a href="../functions/posix_fallocate.html"><i>posix_fallocate</i>()</a>, <a href="../functions/posix_madvise.html"><i>posix_madvise</i>()</a></p></blockquote><h4><a name="tag_13_11_08"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 1. Derived from Issue 1 of the SVID.</p></blockquote><h4><a name="tag_13_11_09"></a>Issue 5</h4><blockquote><p>The DESCRIPTION is updated for alignment with the POSIX Realtime Extension.</p></blockquote><h4><a name="tag_13_11_10"></a>Issue 6</h4><blockquote><p>The following changes are made for alignment with the ISO POSIX-1:1996 standard:</p><ul><li><p>O_DSYNC and O_RSYNC are marked as part of the Synchronized Input and Output option.</p></li></ul><p>The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:</p><ul><li><p>The definition of the <b>mode_t</b>, <b>off_t</b>, and <b>pid_t</b> types is mandated.</p></li></ul><p>The F_GETOWN and F_SETOWN values are added for sockets.</p><p>The <a href="../functions/posix_fadvise.html"><i>posix_fadvise</i>()</a>, <a href="../functions/posix_fallocate.html"><i>posix_fallocate</i>()</a>, and <a href="../functions/posix_madvise.html"><i>posix_madvise</i>()</a> functions are added for alignment withIEEE Std 1003.1d-1999.</p><p>IEEE PASC Interpretation 1003.1 #102 is applied, moving the prototype for <a href="../functions/posix_madvise.html"><i>posix_madvise</i>()</a> to <a href="../basedefs/sys/mman.h.html"><i><sys/mman.h></i></a>.</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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