Hello,

Since linux is file-oriented. Everytime, I want to operate a device, I need to open and close the dev file. Is it good? For example, my application needs to kick the watchdog timer. in my function to kick, I open the dev file, ioctl to kick it and close the file at the end.

I know it works. But I don't think it's good to open/close everytime. I'm wandering how much resource it waste to open/close the file each time? If my harddisk is working very busyily, will the open function be delayed?

I open/close everytime because it's one function. It's easy to be used by other users.

Thanks

If you know your program is going to be calling the function which opens and closes a device file frequently it might make sense to open it globally and used the same opened instance each time.

However, don't confused /dev/ files with real files on a file system somewhere. /dev is a virtual file system that allows you to use filo i/o opperations as hooks into the kernel. That information isn't actually be written or read from the hard disk.

It's the answer that I'm looking for. Thank you very much.