given inode and fs, determine if dir or not?

[Guy Harris]

>Sorry: an int that represents an inode number.

In that case, life gets more complicated; you have to open the file
system (which means you have to figure out which device it is - if you
have only the major/minor, you'd have to scan "/dev" looking for the
appropriate block special file) and decipher the i-list.  This is not
*too* painful for a V7/S5 file system; it's more work for a 4.2BSD file
system.

Note also that if the file system in question is, say, an NFS or RFS
file system, you're probably out of luck.