Obtains a file pathname from the user via the platform-specific standard (modal) dialog, using parent as the parent window if it is specified.
The result is #f if the user cancels the dialog, the selected pathname otherwise. The returned pathname may or may not exist, although the style of the dialog is directed towards creating a new file.
If directory is not #f, it is used as the starting directory for the file selector (otherwise the starting directory is chosen automatically in a platform-specific manner, usually based on the current directory and the user's interactions in previous calls to get-file and put-file). If filename is not #f, it is used as the default filename when appropriate.
Under Windows, if extension is not #f, the returned path will use the extension if the user does not supply one; the extension string should not contain a period. The extension is ignored on other platforms.
The style argument is provided for future extensions. Currently, style must be the empty list.