1<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml"> 4 <head> 5 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> 6 <title>Db::fd()</title> 7 <link rel="stylesheet" href="apiReference.css" type="text/css" /> 8 <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> 9 <link rel="start" href="index.html" title="Berkeley DB C++ API Reference" /> 10 <link rel="up" href="db.html" title="Chapter 2. The Db Handle" /> 11 <link rel="prev" href="dbexists.html" title="Db::exists()" /> 12 <link rel="next" href="dbget.html" title="Db::get()" /> 13 </head> 14 <body> 15 <div class="navheader"> 16 <table width="100%" summary="Navigation header"> 17 <tr> 18 <th colspan="3" align="center">Db::fd()</th> 19 </tr> 20 <tr> 21 <td width="20%" align="left"><a accesskey="p" href="dbexists.html">Prev</a> </td> 22 <th width="60%" align="center">Chapter 2. 23 The Db Handle 24 </th> 25 <td width="20%" align="right"> <a accesskey="n" href="dbget.html">Next</a></td> 26 </tr> 27 </table> 28 <hr /> 29 </div> 30 <div class="sect1" lang="en" xml:lang="en"> 31 <div class="titlepage"> 32 <div> 33 <div> 34 <h2 class="title" style="clear: both"><a id="dbfd"></a>Db::fd()</h2> 35 </div> 36 </div> 37 </div> 38 <pre class="programlisting">#include <db_cxx.h> 39 40int 41Db::fd(int *fdp);</pre> 42 <p> 43 The <code class="methodname">Db::fd()</code> method provides access to a file descriptor 44 representative of the underlying database. A file descriptor 45 referring to the same file will be returned to all processes that call 46 <a class="xref" href="dbopen.html" title="Db::open()">Db::open()</a> with the same 47 <span class="bold"><strong>file</strong></span> parameter. 48 </p> 49 <p> 50 This file descriptor may be safely used as a parameter to the 51 <span class="bold"><strong>fcntl</strong></span>(2) and <span class="bold"><strong>flock</strong></span>(2) locking functions. 52 </p> 53 <p> 54 The <code class="methodname">Db::fd()</code> method only supports a coarse-grained form of locking. 55 Applications should instead use the Berkeley DB lock manager where 56 possible. 57 </p> 58 <p> 59 The <code class="methodname">Db::fd()</code> <span> 60 61 <span> 62 method either returns a non-zero error value or throws an 63 exception that encapsulates a non-zero error value on 64 failure, and returns 0 on success. 65 </span> 66 </span> 67 </p> 68 <div class="sect2" lang="en" xml:lang="en"> 69 <div class="titlepage"> 70 <div> 71 <div> 72 <h3 class="title"><a id="id1633577"></a>Parameters</h3> 73 </div> 74 </div> 75 </div> 76 <div class="sect3" lang="en" xml:lang="en"> 77 <div class="titlepage"> 78 <div> 79 <div> 80 <h4 class="title"><a id="id1634058"></a>fdp</h4> 81 </div> 82 </div> 83 </div> 84 <p> 85 The <span class="bold"><strong>fdp</strong></span> parameter references memory 86 into which the current file descriptor is copied. 87 </p> 88 </div> 89 </div> 90 <div class="sect2" lang="en" xml:lang="en"> 91 <div class="titlepage"> 92 <div> 93 <div> 94 <h3 class="title"><a id="id1634363"></a>Class</h3> 95 </div> 96 </div> 97 </div> 98 <p> 99 <a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a> 100 </p> 101 </div> 102 <div class="sect2" lang="en" xml:lang="en"> 103 <div class="titlepage"> 104 <div> 105 <div> 106 <h3 class="title"><a id="id1634204"></a>See Also</h3> 107 </div> 108 </div> 109 </div> 110 <p> 111 <a class="xref" href="db.html#dblist" title="Database and Related Methods">Database and Related Methods</a> 112 </p> 113 </div> 114 </div> 115 <div class="navfooter"> 116 <hr /> 117 <table width="100%" summary="Navigation footer"> 118 <tr> 119 <td width="40%" align="left"><a accesskey="p" href="dbexists.html">Prev</a> </td> 120 <td width="20%" align="center"> 121 <a accesskey="u" href="db.html">Up</a> 122 </td> 123 <td width="40%" align="right"> <a accesskey="n" href="dbget.html">Next</a></td> 124 </tr> 125 <tr> 126 <td width="40%" align="left" valign="top">Db::exists() </td> 127 <td width="20%" align="center"> 128 <a accesskey="h" href="index.html">Home</a> 129 </td> 130 <td width="40%" align="right" valign="top"> Db::get()</td> 131 </tr> 132 </table> 133 </div> 134 </body> 135</html> 136