Directory Overview

• To keep track of files, file systems normally have directories or folders. Usually, a directory is itself a file.
• The directory can be viewed as a symbol table that translates file names into their directory entries.
• A typical directory entry contains information (attributes, location, ownership) about a file.
• We want to be able
  • to insert entries,
  • to delete entries,
  • to search for a named entry,
  • to list all the entries in the directory.
• When considering a particular directory structure! we need to keep in mind the operations that are to be performed on a directory:
  • Search for a file. We need to be able to search a directory structure to find the entry for a particular file.
  • Create a file. New files need to be created and added to the directory.
  • Delete a file. When a file is no longer needed, we want to be able to remove it from the directory.
  • List a directory. We need to be able to list the files in a directory and the contents of the directory entry for each file in the list.
  • Rename a file. Because the name of a file represents its contents to its users, we must be able to change the name when the contents or use of the file changes.
  • Traverse the file system. We may wish to access every directory and every file within a directory structure. For reliability, it is a good idea to save the contents and structure of the entire file system at regular intervals (backup copy).