Originally Posted by
matsp
I'm pretty sure you can figure out a temporal value of the free space - I say temporal, since it will not necessarily stay that way if some other process is also writing to the same device. The command "df" in Linux/Unix tells you how much space is available on a disk, and you should be able to use whatever system operations that it uses to find the same information, and I'm sure the NTFS driver has a way to deliver how much free space it thinks there is on the disk. Sorry, I don't KNOW the answer to what system operation actually gets that information from the driver to the user-level code, and a quick google doesn't reveal much useful info - perhaps "strace df ." will give a better lead onto the "disk free space" quest - unfortunately, I haven't got a Linux system up and running right now.
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Mats