GetDiskSpaceAvailable in Linux

Hi,

I want to check the available space on the disk......
this is how i am doing it............


PRInt64 iSize = 0;
nsCOMPtr<nsILocalFile> mFile;
NS_NewLocalFile (path, PR_TRUE, getter_AddRefs (mFile));
mFile->GetDiskSpaceAvailable(&iSize);


I get the correct values on Windows......but on the linux the
available disk space i get is 0.
Can anyone help me on this.......


Thanks in Advance
Vineeth Aravindakshan