Listing 1. Pseudo-code for opening a file.

Put the starting directory in DIR.
Put the pathname in PATH.
While (PATH has one than one component)
    Take one component off PATH.
    Find that component in DIR yielding the INODE.
    If (permissions on INODE are not OK)
        Return ERROR
    Set DIR = INODE
End-While
Take the last component off PATH yielding FILENAME.
Find FILENAME in DIR yielding INODE.
If (permission on INODE are not OK)
     Return ERROR
Store INODE with the process for quick later lookup.
Return SUCCESS.