[工学]ch10.ppt

* * * * Windows XP Access-control List Management A Sample UNIX Directory Listing End of Chapter 10 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 10.* Silberschatz, Galvin and Gagne ?2005 Operating System Concepts – 7th Edition, Jan 1, 2005 Chapter 10: File-System Interface File Concept Access Methods Directory Structure File-System Mounting File Sharing 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 File Concept Contiguous logical address space Types: Data numeric character binary 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 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 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 Open Files Several pieces of data are needed to manage open files: File pointer: pointer to last read/write location, per process that has the file open File-open count: counter of number of