上海交通大学：《操作系统 Operating System》课程教学资源（课件讲稿）OS-Lec21_file system interface

CHAPTER 10:FILE-SYSTEM INTERFACE

CHAPTER 10: FILE-SYSTEM INTERFACE

CHAPTER 10:FILE-SYSTEM INTERFACE o File Concept o Access Methods o Directory Structure o File-System Mounting o File Sharing o Protection

CHAPTER 10: FILE-SYSTEM INTERFACE  File Concept  Access Methods  Directory Structure  File-System Mounting  File Sharing  Protection

OBJECTIVES o To explain the function of file systems o To describe the interfaces to file systems o To discuss file-system design tradeoffs, including access methods,file sharing,file locking,and directory structures o To explore file-system protection

OBJECTIVES  To explain the function of file systems  To describe the interfaces to file systems  To discuss file-system design tradeoffs, including access methods, file sharing, file locking, and directory structures  To explore file-system protection

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DISK

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Symbolic Open Levels of file name file ID abstraction USER File system interface Files/ directories Directory High-level file and FS management directory functions Logcal block# Basic file system Open/close functions Physical device address Device organization Low-level data methods access functions 1O system interface Logical block# 6

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FILE CONCEPT o Contiguous logical address space o Types: ·Data o numeric o character o binary ·Program

FILE CONCEPT  Contiguous logical address space  Types:  Data  numeric  character  binary  Program

FILE STRUCTURE o None-sequence of words,bytes o Simple record structure 。Lines 。Fixed length ·Variable length o Complex Structures ·Formatted document Relocatable load file o Can simulate last two with first method by inserting appropriate control characters o Who decides: ·Operating system Program

FILE STRUCTURE  None - sequence of words, bytes  Simple record structure  Lines  Fixed length  Variable length  Complex Structures  Formatted document  Relocatable load file  Can simulate last two with first method by inserting appropriate control characters  Who decides:  Operating system  Program

FILE ATTRIBUTES o Name-only information kept in human-readable form o Identifier-unique tag(number)identifies file within file system o Type-needed for systems that support different types o Location-pointer to file location on device o Size-current file size o Protection-controls who can do reading,writing, executing o Time,date,and user identification-data for protection,security,and usage monitoring o Information about files are kept in the directory structure, which is maintained on the disk

FILE ATTRIBUTES  Name – only information kept in human-readable form  Identifier – unique tag (number) identifies file within file system  Type – needed for systems that support different types  Location – pointer to file location on device  Size – current file size  Protection – controls who can do reading, writing, executing  Time, date, and user identification – data for protection, security, and usage monitoring  Information about files are kept in the directory structure, which is maintained on the disk

FILE OPERATIONS o File is an abstract data type o Create o Write o Read o Reposition within file o Delete o Truncate o Open(F:)-search the directory structure on disk for entry F;,and move the content of entry to memory o Close (F)-move the content of entry F;in memory to directory structure on disk

FILE OPERATIONS  File is an abstract data type  Create  Write  Read  Reposition within file  Delete  Truncate  Open(Fi ) – search the directory structure on disk for entry Fi , and move the content of entry to memory  Close (Fi ) – move the content of entry Fi in memory to directory structure on disk