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 selecting existing files.
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.