This is possible in Flash 10.
Take a look at the FileReference class, specifically the save method.
There are certain limitations imposed for security's sake, of course.
The write can only be initiated by user interaction (e.g. a button click), and it will always pop up the host OS's File Save dialog box prompting the user to choose a location (or cancel).
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…