distinguishing standard file descriptors from others

[<sudheer.divakaran@xxxxxxxxx>]

Title: distinguishing standard file descriptors from others

Hi,
  Is it possible to distinguish standard file descriptors (0,1,2) from others from the structures like struct file,struct vfsmount etc?.

For e.g., say descriptor 0 points to a normal file instead of stdin, then I should be able to distinguish it.

Thanks
Sudheer