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<a href="intro.html"><h2>SQLite C Interface</h2></a><h2>Initialize The SQLite Library</h2><blockquote><pre>int sqlite3_initialize(void);
int sqlite3_shutdown(void);
int sqlite3_os_init(void);
int sqlite3_os_end(void);
</pre></blockquote><p>
The sqlite3_initialize() routine initializes the
SQLite library. The sqlite3_shutdown() routine
deallocates any resources that were allocated by sqlite3_initialize().
These routines are designed to aid in process initialization and
shutdown on embedded systems. Workstation applications using
SQLite normally do not need to invoke either of these routines.</p>
<p>A call to sqlite3_initialize() is an "effective" call if it is
the first time sqlite3_initialize() is invoked during the lifetime of
the process, or if it is the first time sqlite3_initialize() is invoked
following a call to sqlite3_shutdown(). Only an effective call
of sqlite3_initialize() does any initialization. All other calls
are harmless no-ops.</p>
<p>A call to sqlite3_shutdown() is an "effective" call if it is the first
call to sqlite3_shutdown() since the last sqlite3_initialize(). Only
an effective call to sqlite3_shutdown() does any deinitialization.
All other valid calls to sqlite3_shutdown() are harmless no-ops.</p>
<p>The sqlite3_initialize() interface is threadsafe, but sqlite3_shutdown()
is not. The sqlite3_shutdown() interface must only be called from a
single thread. All open <a href="../c3ref/sqlite3.html">database connections</a> must be closed and all
other SQLite resources must be deallocated prior to invoking
sqlite3_shutdown().</p>
<p>Among other things, sqlite3_initialize() will invoke
sqlite3_os_init(). Similarly, sqlite3_shutdown()
will invoke sqlite3_os_end().</p>
<p>The sqlite3_initialize() routine returns <a href="../rescode.html#ok">SQLITE_OK</a> on success.
If for some reason, sqlite3_initialize() is unable to initialize
the library (perhaps it is unable to allocate a needed resource such
as a mutex) it returns an <a href="../rescode.html">error code</a> other than <a href="../rescode.html#ok">SQLITE_OK</a>.</p>
<p>The sqlite3_initialize() routine is called internally by many other
SQLite interfaces so that an application usually does not need to
invoke sqlite3_initialize() directly. For example, <a href="../c3ref/open.html">sqlite3_open()</a>
calls sqlite3_initialize() so the SQLite library will be automatically
initialized when <a href="../c3ref/open.html">sqlite3_open()</a> is called if it has not be initialized
already. However, if SQLite is compiled with the <a href="../compile.html#omit_autoinit">SQLITE_OMIT_AUTOINIT</a>
compile-time option, then the automatic calls to sqlite3_initialize()
are omitted and the application must call sqlite3_initialize() directly
prior to using any other SQLite interface. For maximum portability,
it is recommended that applications always invoke sqlite3_initialize()
directly prior to using any other SQLite interface. Future releases
of SQLite may require this. In other words, the behavior exhibited
when SQLite is compiled with <a href="../compile.html#omit_autoinit">SQLITE_OMIT_AUTOINIT</a> might become the
default behavior in some future release of SQLite.</p>
<p>The sqlite3_os_init() routine does operating-system specific
initialization of the SQLite library. The sqlite3_os_end()
routine undoes the effect of sqlite3_os_init(). Typical tasks
performed by these routines include allocation or deallocation
of static resources, initialization of global variables,
setting up a default <a href="../c3ref/vfs.html">sqlite3_vfs</a> module, or setting up
a default configuration using <a href="../c3ref/config.html">sqlite3_config()</a>.</p>
<p>The application should never invoke either sqlite3_os_init()
or sqlite3_os_end() directly. The application should only invoke
sqlite3_initialize() and sqlite3_shutdown(). The sqlite3_os_init()
interface is called automatically by sqlite3_initialize() and
sqlite3_os_end() is called by sqlite3_shutdown(). Appropriate
implementations for sqlite3_os_init() and sqlite3_os_end()
are built into SQLite when it is compiled for Unix, Windows, or OS/2.
When <a href="../custombuild.html">built for other platforms</a>
(using the <a href="../compile.html#os_other">SQLITE_OS_OTHER=1</a> compile-time
option) the application must supply a suitable implementation for
sqlite3_os_init() and sqlite3_os_end(). An application-supplied
implementation of sqlite3_os_init() or sqlite3_os_end()
must return <a href="../rescode.html#ok">SQLITE_OK</a> on success and some other <a href="../rescode.html">error code</a> upon
failure.
</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>
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