MECH 2301 Lecture 19: MECH 2301 Lecture 19 Notes
20 May 2018
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MECH 2301 Lecture 19 Notes
Introduction
Utilities Load the Entire File
• UNIX proides a additioal ild card for, [choices].
• For example, [aeiou] would look for a file name with a single letter a, e, i, o, or u in the
given position.
• [a-zA-Z]* would accept zero or more uppercase or lowercase letters, but no numbers, in
the given position.
• In addition, many systems provide file utilities within the command structure that call
upon the file management system for support.
• Sport utilities sort the records within a file by key field or by some other positional
indicator.
• Some sort utilities load the entire file into memory, while others retrieve and store
records one by one.
• In both cases, the file management system is used to perform the actual file and record
retrieval and storage.
• Other examples of utilities commonly provided include utilities to merge two files
record by record and to compare two files record by record.
• The file management system is directly responsible for all aspects of the maintenance of
the file system.
• This requires the file system to perform five major functions
• The file management system provides the connection between the logical file systems
with its physical implementation, allowing the physical view to remain essentially
invisible.
• It creates a logical view for the user, masks the physical view, and provides the mapping
between the two views.
• Stating this more informally, the user requests a file by name, and the file is retrieved
• The user does not know where the file is actually stored, nor does he or she care.
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