EECS 1012 Lecture Notes - Lecture 10: Hard Link, Inode
13 Jun 2018
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EECS 1012 Lecture 10 Notes
Introduction
File temporarily
• Under certain conditions, the changes made by user 2 will destroy the changes made by
user 1.
• A system for locking the file temporarily to prevent this type of error is required.
• Further discussion of locking is outside the scope.
• As you can see, there are difficulties and dangers in providing and using acyclic-graph
directories.
• Many system designers feel that the advantages outweigh the disadvantages, however.
• UNIX and the Macintosh both support acyclic-graph directories.
• Macintosh links are called aliases.
• The Macintosh uses a simple implementation.
• An alias is a hard-coded link that points to the original file.
• If the original file is moved or deleted, use of the link will cause an error.
• The Macintosh does not check for the presence of cycles
• However, the visual nature of the Macintosh interface makes cycles less likely to occur
and less problematic.
• The search operations that can cause loops are instead performed visually, and there is
no reason for the user to continue opening folders beyond a point of usefulness.
• Windows implements links similarly with shortcuts.
• UNIX provides two different kinds of links.
• The difference between them is shown
• A hard link points from a new directory entry to the same i-node as another directory
entry somewhere in the file system.
• Since both entries point to the same i-node, any changes made in the file are
automatically reflected to both.
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