I write a cron job to download a DVD iso file (about 2G) from a ftp site every day. But the creat of the iso file need a lot of time so I need to check the file is integrated. The meothod I use is that check the size of the file and sleep 10s then check the size of the file secondly. If the size of the file is not changed, the iso file is integrated. I feel my method is not elegant. Is there better ways to solve the program?