Well, go for it!
Since you didn't ask a question, that's about all we can say. But just out of curiosity, what exactly do you mean? "first data" -- first M bytes of each record? first N records? first M bytes of first N records? If you do post a question, you'll need to carefully consider what to post since we do not know what you've tried, what you want to do, nor do we know anything about your files and their processing.