Writes a resource value into the resource database (for example, ``WIN.INI'', or ``.Xdefaults''). If file is null, the platform-specific default resource file is used.
Under X, the resource databases are cached until exit, when all updated resource databases are written to their files. Note that it is considered bad manners to write to the ``.Xdefaults'' file under X Windows, although the ``WIN.INI'' file is fair game under Windows.
See also wx:get-resource.