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_create</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="dbclose.html" title="DB->close()" /> 12 <link rel="next" href="dbcompact.html" title="DB->compact()" /> 13 </head> 14 <body> 15 <div class="navheader"> 16 <table width="100%" summary="Navigation header"> 17 <tr> 18 <th colspan="3" align="center">db_create</th> 19 </tr> 20 <tr> 21 <td width="20%" align="left"><a accesskey="p" href="dbclose.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="dbcompact.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="dbcreate"></a>db_create</h2> 35 </div> 36 </div> 37 </div> 38 <pre class="programlisting">#include <db.h> 39 40int db_create(DB **dbp, DB_ENV *dbenv, u_int32_t flags); </pre> 41 <p> 42 The <code class="function">db_create()</code> function creates a <a class="link" href="db.html" title="Chapter��2.�� The DB Handle">DB</a> 43 structure that is the handle for a Berkeley DB database. This function allocates memory for the 44 structure, returning a pointer to the structure in the memory to which 45 <span class="bold"><strong>dbp</strong></span> refers. To release the allocated memory and 46 discard the handle, call the <a class="xref" href="dbclose.html" title="DB->close()">DB->close()</a>, 47 <a class="xref" href="dbremove.html" title="DB->remove()">DB->remove()</a>, 48 <a class="xref" href="dbrename.html" title="DB->rename()">DB->rename()</a>, or 49 <a class="xref" href="dbverify.html" title="DB->verify()">DB->verify()</a> methods. 50 </p> 51 <p> 52 DB handles are free-threaded if the 53 <a class="link" href="envopen.html#envopen_DB_THREAD">DB_THREAD</a> flag is specified to 54 the <a class="xref" href="dbopen.html" title="DB->open()">DB->open()</a> method when the database is opened or 55 if the database environment in which the database is opened is free-threaded. The handle 56 should not be closed while any other handle that refers to the database is in use; for 57 example, database handles must not be closed while cursor handles into the database remain 58 open, or transactions that include operations on the database have not yet been committed 59 or aborted. Once the <a class="xref" href="dbclose.html" title="DB->close()">DB->close()</a>, 60 <a class="xref" href="dbremove.html" title="DB->remove()">DB->remove()</a>, 61 <a class="xref" href="dbrename.html" title="DB->rename()">DB->rename()</a>, or 62 <a class="xref" href="dbverify.html" title="DB->verify()">DB->verify()</a> 63 methods are called, the handle may not be accessed again, regardless of the method's return. 64 </p> 65 <p> 66 The DB handle contains a special field, <code class="literal">app_private</code>, 67 which is declared as type <code class="literal">void *</code>. This field is provided for the use 68 of the application program. It is initialized to NULL and is not further used by 69 Berkeley DB in any way. 70 </p> 71 <p> 72 The <code class="literal">db_create</code> function returns a non-zero error value on failure 73 and 0 on success. 74 </p> 75 <div class="sect2" lang="en" xml:lang="en"> 76 <div class="titlepage"> 77 <div> 78 <div> 79 <h3 class="title"><a id="id1632467"></a>Parameters</h3> 80 </div> 81 </div> 82 </div> 83 <div class="sect3" lang="en" xml:lang="en"> 84 <div class="titlepage"> 85 <div> 86 <div> 87 <h4 class="title"><a id="id1632665"></a>dbp</h4> 88 </div> 89 </div> 90 </div> 91 <p> 92 The <span class="bold"><strong>dbp</strong></span> parameter references the 93 memory into which the returned structure pointer is stored. 94 </p> 95 </div> 96 <div class="sect3" lang="en" xml:lang="en"> 97 <div class="titlepage"> 98 <div> 99 <div> 100 <h4 class="title"><a id="id1632600"></a>dbenv</h4> 101 </div> 102 </div> 103 </div> 104 <p> 105 <span>If the <span class="bold"><strong>dbenv</strong></span> parameter is NULL,</span> 106 107 the database is standalone; that is, it is not part of any Berkeley DB 108 environment. 109 </p> 110 <p> 111 <span> 112 If the <span class="bold"><strong>dbenv</strong></span> parameter is not NULL, 113 </span> 114 115 the database is created within the specified Berkeley DB environment. 116 The database access methods automatically make calls to the other 117 subsystems in Berkeley DB, based on the enclosing environment. For 118 example, if the environment has been configured to use locking, the 119 access methods will automatically acquire the correct locks when 120 reading and writing pages of the database. 121 </p> 122 </div> 123 <div class="sect3" lang="en" xml:lang="en"> 124 <div class="titlepage"> 125 <div> 126 <div> 127 <h4 class="title"><a id="id1632578"></a>flags</h4> 128 </div> 129 </div> 130 </div> 131 <p> 132 The <span class="bold"><strong>flags</strong></span> parameter is currently 133 unused, and must be set to 0. 134 </p> 135 <div class="itemizedlist"> 136 <ul type="disc"></ul> 137 </div> 138 </div> 139 </div> 140 <div class="sect2" lang="en" xml:lang="en"> 141 <div class="titlepage"> 142 <div> 143 <div> 144 <h3 class="title"><a id="id1632748"></a>Errors</h3> 145 </div> 146 </div> 147 </div> 148 <p> 149 The <code class="function">db_create()</code> function may fail and return one of the following non-zero 150 errors: 151 </p> 152 <div class="sect3" lang="en" xml:lang="en"> 153 <div class="titlepage"> 154 <div> 155 <div> 156 <h4 class="title"><a id="id1632410"></a>EINVAL</h4> 157 </div> 158 </div> 159 </div> 160 <p> 161 An invalid flag value or parameter was specified. 162 </p> 163 </div> 164 </div> 165 <div class="sect2" lang="en" xml:lang="en"> 166 <div class="titlepage"> 167 <div> 168 <div> 169 <h3 class="title"><a id="id1632411"></a>Class</h3> 170 </div> 171 </div> 172 </div> 173 <p> 174 <a class="link" href="db.html" title="Chapter��2.�� The DB Handle">DB</a> 175 </p> 176 </div> 177 <div class="sect2" lang="en" xml:lang="en"> 178 <div class="titlepage"> 179 <div> 180 <div> 181 <h3 class="title"><a id="id1632381"></a>See Also</h3> 182 </div> 183 </div> 184 </div> 185 <p> 186 <a class="xref" href="db.html#dblist" title="Database and Related Methods">Database and Related Methods</a> 187 </p> 188 </div> 189 </div> 190 <div class="navfooter"> 191 <hr /> 192 <table width="100%" summary="Navigation footer"> 193 <tr> 194 <td width="40%" align="left"><a accesskey="p" href="dbclose.html">Prev</a>��</td> 195 <td width="20%" align="center"> 196 <a accesskey="u" href="db.html">Up</a> 197 </td> 198 <td width="40%" align="right">��<a accesskey="n" href="dbcompact.html">Next</a></td> 199 </tr> 200 <tr> 201 <td width="40%" align="left" valign="top">DB->close()��</td> 202 <td width="20%" align="center"> 203 <a accesskey="h" href="index.html">Home</a> 204 </td> 205 <td width="40%" align="right" valign="top">��DB->compact()</td> 206 </tr> 207 </table> 208 </div> 209 </body> 210</html> 211