用inotify写的，监视机顶盒/mnt/OTG目录，U盘自动运行程序，运行U盘根目录中的update.sh脚本，进行机顶盒升级-write with the inotify function family, monitor the "/mnt/OTG" directory of a set-top-box, automatically run the scr ipt "update.sh" in that directory which is mounted with Udisk