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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"><html><head><title>Virtual File System Objects</title><style type="text/css">body { margin: auto; font-family: "Verdana" "sans-serif"; padding: 8px 1%;}a { color: #45735f }a:visited { color: #734559 }.logo { position:absolute; margin:3px; }.tagline { float:right; text-align:right; font-style:italic; width:240px; margin:12px; margin-top:58px;}.toolbar { font-variant: small-caps; text-align: center; line-height: 1.6em; margin: 0; padding:1px 8px;}.toolbar a { color: white; text-decoration: none; padding: 6px 12px; }.toolbar a:visited { color: white; }.toolbar a:hover { color: #80a796; background: white; }.content { margin: 5%; }.content dt { font-weight:bold; }.content dd { margin-bottom: 25px; margin-left:20%; }.content ul { padding:0px; padding-left: 15px; margin:0px; }/* rounded corners */.se { background: url(../images/se.png) 100% 100% no-repeat #80a796}.sw { background: url(../images/sw.png) 0% 100% no-repeat }.ne { background: url(../images/ne.png) 100% 0% no-repeat }.nw { background: url(../images/nw.png) 0% 0% no-repeat }</style><meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head><body><div><!-- container div to satisfy validator --><a href="../index.html"><img class="logo" src="../images/SQLite.gif" alt="SQLite Logo" border="0"></a><div><!-- IE hack to prevent disappearing logo--></div><div class="tagline">Small. Fast. Reliable.<br>Choose any three.</div><table width=100% style="clear:both"><tr><td> <div class="se"><div class="sw"><div class="ne"><div class="nw"> <div class="toolbar"> <a href="../about.html">About</a> <a href="../sitemap.html">Sitemap</a> <a href="../docs.html">Documentation</a> <a href="../download.html">Download</a> <a href="../copyright.html">License</a> <a href="../news.html">News</a> <a href="http://www.sqlite.org/cvstrac/index">Developers</a> <a href="../support.html">Support</a> </div></div></div></div></div></td></tr></table> <a href="intro.html"><h2>SQLite C Interface</h2></a><h2>Virtual File System Objects</h2><blockquote><pre>sqlite3_vfs *sqlite3_vfs_find(const char *zVfsName);int sqlite3_vfs_register(sqlite3_vfs*, int makeDflt);int sqlite3_vfs_unregister(sqlite3_vfs*);</pre></blockquote><p>A virtual filesystem (VFS) is an <a href="../c3ref/vfs.html">sqlite3_vfs</a> objectthat SQLite uses to interactwith the underlying operating system. Most SQLite builds come with asingle default VFS that is appropriate for the host computer.New VFSes can be registered and existing VFSes can be unregistered.The following interfaces are provided.</p><p>The sqlite3_vfs_find() interface returns a pointer toa VFS given its name. Names are case sensitive.Names are zero-terminated UTF-8 strings.If there is no match, a NULLpointer is returned. If zVfsName is NULL then the defaultVFS is returned.</p><p>New VFSes are registered with sqlite3_vfs_register().Each new VFS becomes the default VFS if the makeDflt flag is set.The same VFS can be registered multiple times without injury.To make an existing VFS into the default VFS, register it againwith the makeDflt flag set. If two different VFSes with thesame name are registered, the behavior is undefined. If aVFS is registered with a name that is NULL or an empty string,then the behavior is undefined.</p><p>Unregister a VFS with the sqlite3_vfs_unregister() interface.If the default VFS is unregistered, another VFS is chosen asthe default. The choice for the new VFS is arbitrary.</p><p><h3>Invariants:</h3><table border="0" cellpadding="5" cellspacing="0"><tr><td valign="top">F11203</td> <td valign="top">The <a href="../c3ref/vfs_find.html">sqlite3_vfs_find(N)</a> interface returns a pointer to theregistered <a href="../c3ref/vfs.html">sqlite3_vfs</a> object whose name exactly matchesthe zero-terminated UTF-8 string N, or it returns NULL ifthere is no match.</td></tr><tr><td valign="top">F11206</td> <td valign="top">If the N parameter to <a href="../c3ref/vfs_find.html">sqlite3_vfs_find(N)</a> is NULL thenthe function returns a pointer to the default <a href="../c3ref/vfs.html">sqlite3_vfs</a>object if there is one, or NULL if there is no default<a href="../c3ref/vfs.html">sqlite3_vfs</a> object.</td></tr><tr><td valign="top">F11209</td> <td valign="top">The <a href="../c3ref/vfs_find.html">sqlite3_vfs_register(P,F)</a> interface registers thewell-formed <a href="../c3ref/vfs.html">sqlite3_vfs</a> object P using the name givenby the zName field of the object.</td></tr><tr><td valign="top">F11212</td> <td valign="top">Using the <a href="../c3ref/vfs_find.html">sqlite3_vfs_register(P,F)</a> interface to registerthe same <a href="../c3ref/vfs.html">sqlite3_vfs</a> object multiple times is a harmless no-op.</td></tr><tr><td valign="top">F11215</td> <td valign="top">The <a href="../c3ref/vfs_find.html">sqlite3_vfs_register(P,F)</a> interface makes thethe <a href="../c3ref/vfs.html">sqlite3_vfs</a> object P the default <a href="../c3ref/vfs.html">sqlite3_vfs</a> objectif F is non-zero.</td></tr><tr><td valign="top">F11218</td> <td valign="top">The <a href="../c3ref/vfs_find.html">sqlite3_vfs_unregister(P)</a> interface unregisters the<a href="../c3ref/vfs.html">sqlite3_vfs</a> object P so that it is no longer returned bysubsequent calls to <a href="../c3ref/vfs_find.html">sqlite3_vfs_find()</a>.</td></tr></table></p><p>See also lists of <a href="objlist.html">Objects</a>, <a href="constlist.html">Constants</a>, and <a href="funclist.html">Functions</a>.</p><hr><small><i>This page last modified 2008/05/12 13:08:44 UTC</i></small></div></body></html>⌨️ 快捷键说明
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