Links

Provide a reference to a directory in another part of the tree or a file in another directory - allows alternative names for the same file

• Hard Link : references address of the file (only for files in Unix)
• Symbolic Link : references full path name of file (or directory in Unix)
• Two types : Cyclic or acyclic linkages
• sometimes links across file systems not allowed

  
Figure 3: (a) Acyclic graph directory ; (b) Cyclic graph directory

• Problems : File Deletion :
  Search for links and remove them
  Leave links (causes exception when used e.g. symbolic links, Mac aliases)
  Keep link count with file - delete when count =0 (e.g. hard links)
• Loops : Directory traversal algorithm may loop (in archiving utilities for instance) - in cyclic graph directories