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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
![figure122](img3.gif)
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
Omer F Rana
Sat Feb 15 19:06:41 GMT 1997