SQLITE_EXTERN char *sqlite3_temp_directory;
If this global variable is made to point to a string which is the name of a folder (a.k.a. directory), then all temporary files created by SQLite when using a built-in VFS will be placed in that directory. If this variable is a NULL pointer, then SQLite performs a search for an appropriate temporary file directory.
It is not safe to read or modify this variable in more than one thread at a time. It is not safe to read or modify this variable if a database connection is being used at the same time in a separate thread. It is intended that this variable be set once as part of process initialization and before any SQLite interface routines have been called and that this variable remain unchanged thereafter.
The temp_store_directory pragma may modify this variable and cause it to point to memory obtained from sqlite3_malloc. Furthermore, the temp_store_directory pragma always assumes that any string that this variable points to is held in memory obtained from sqlite3_malloc and the pragma may attempt to free that memory using sqlite3_free. Hence, if this variable is modified directly, either it should be made NULL or made to point to memory obtained from sqlite3_malloc or else the use of the temp_store_directory pragma should be avoided.
Note to Windows Runtime users: The temporary directory must be set prior to calling sqlite3_open or sqlite3_open_v2. Otherwise, various features that require the use of temporary files may fail. Here is an example of how to do this using C++ with the Windows Runtime:
LPCWSTR zPath = Windows::Storage::ApplicationData::Current-> TemporaryFolder->Path->Data(); char zPathBuf[MAX_PATH + 1]; memset(zPathBuf, 0, sizeof(zPathBuf)); WideCharToMultiByte(CP_UTF8, 0, zPath, -1, zPathBuf, sizeof(zPathBuf), NULL, NULL); sqlite3_temp_directory = sqlite3_mprintf("%s", zPathBuf);