Links

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Links

• Hard Link
• Symbolic Link

2
Linking Files

• Since UNIX is a multi-user operating system, it
  makes sense to allow users to share files to
  collaborate on projects (such as programming
  projects, reports, etc.)

3
Linking Files

• In order to avoid duplication and inefficiency
• it is better to provide links between files to
  give user illusion that what is edited on their
  file affects contents on other groups files.

4
File ID

• Each file contains information regarding the file
  itself file identification
• This information is called i-node number. To view
  i-node information, you can issue the UNIX
  command
• ls -i
• 705900 testone706640 letter2703817 memo1

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Hard Link

• 1. Hard Link
• ln existing_file linked_file
• -pointer to a file
• A directory entry containing the same i-node
  number of a file. All files have at least one
  hard-link - when removed, the link is removed

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Symbolic (soft) Link

• 2. Symbolic Link
• ln -s existing_file linked_file
• - indirect pointer to a file
• A directory entry containing pathname to file
  (i.e. a pointer). Unlike hard links, i-node
  numbers can be different, but possess other
  useful features.

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Hard Link Features

• Disadvantage
• Cannot make hard links to directories(except the
  superuser)
• Cannot cross different file systems
• Advantage
• When original file that other users linked to
  is removed linked file(s) will still exist.

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Symbolic (soft) Link Features

• Advantage
• Can be used by users to link directories
• Can link across different file systems
• Disadvantage
• Symbolic links do not have the same status (legal
  names vs pseudonyms)
• Linked file will be removed if the original file
  removed

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