Yes, correctly it should be 8.3 short name, however, I've no idea which function can be used to convert a full filename into 8.3 on non windows OS. So I just copy the first 13 characters. Do you have any suggestion here to realize 8.3 on other OS. 
PS: jpcsp gays did the same as I did here, just copy the first 13 chars and uppercase it. I know it's not really right.