File management53(1)
- 1. File Management Organization of data - Creating a file - Storing a file in required directory - Removing a file - Opening a file - Closing a file - Maintaining of file details - Name, Type, location, size , date and time of creation or modification - File Protection http://raj-os.blogspot.in/ 1
- 2. File Attributes - Name - Type - Location - Size - Protection - Time, Date and User Identification http://raj-os.blogspot.in/ 2
- 3. File Attributes Name - Given by the user - Only information that is kept in human readable form Type - Information required by systems that support different types http://raj-os.blogspot.in/ 3
- 4. File attributes Location - A pointer to a device and to the location of the file on that device Size - Current size of file (in bytes or words ) - Max size allowed http://raj-os.blogspot.in/ 4
- 5. File Attributes Protection - Access control information ( read, write and execute privileges ) http://raj-os.blogspot.in/ 5
- 6. File Attributes Time, date and user identification - Creation - Last modification - Last use (Useful for protection, security and usage monitoring ) http://raj-os.blogspot.in/ 6
- 7. Basic File Operations ( Minimal Set ) 1. Creating a file 2. Repositioning within a file 3. Deleting a file 4. Truncating a file 5. Reading a file 6. Writing a file http://raj-os.blogspot.in/ 7
- 8. Basic File Operations 1. Creating a file • Allocation of space for the file in the file system • Making an entry for the new file in the directory http://raj-os.blogspot.in/ 8
- 9. Basic File Operations 2. Writing a file • Use a system call specifying - Name of the file - Information to be written • Search directory for the associated entry • Keep a write pointer • Update write pointer after every write http://raj-os.blogspot.in/ 9
- 10. Basic File Operations 3. Reading a file • Use a system call specifying - Name of the file - Address where to put the contents read • Search directory for the associated entry • Keep a read pointer • Update read pointer after every read http://raj-os.blogspot.in/ 10
- 11. Basic File Operations 4. Repositioning within a file • Also known as file seek operation • Search directory for the appropriate entry • Set current-file-position to a given value http://raj-os.blogspot.in/ 11
- 12. Basic File Operations 5.Deleting a file • Search the directory for the named file • Release all file space • Erase the directory entry http://raj-os.blogspot.in/ 12
- 13. Basic File Operations 6. Truncating a file • File contents erased • Name and attributes of file unchanged http://raj-os.blogspot.in/ 13
- 14. Other File Operations • Appending • Renaming Appending Add some information at the end of the file Renaming Name of file changed All other attributes unchanged http://raj-os.blogspot.in/ 14
- 15. Basic file operations can be combined to implement other operations Ex : Creating a copy of a file - Create a new file - Read from old file - Write to new file http://raj-os.blogspot.in/ 15
- 16. Other Desirable Operations Allow the user to get and set the various attributes of a file Ex : i) get the file length ii) set file attributes like file’s owner http://raj-os.blogspot.in/ 16
- 17. Other Desirable Operations Most file operations involve searching the directory for the entry associated with the named file http://raj-os.blogspot.in/ 17
- 18. To Avoid Constant Searching • Many systems open a file when file first is used • The operating system keeps a small table called the Open file table • Open file table contains information about open files • When a file operation is requested, an index into the open file table is used http://raj-os.blogspot.in/ 18
- 19. Other File Operations When a file is no longer actively used, it is closed by the process and the O.S. removes its entry in the Open file table http://raj-os.blogspot.in/ 19
- 20. Other File Operations • Some systems implicitly open a file when it is first referenced • Close it automatically when the program that opened the file terminates http://raj-os.blogspot.in/ 20
- 21. Other File Operations Most systems require that a file be opened explicitly by the programmer with a system call ( open ) before that file can be used http://raj-os.blogspot.in/ 21
- 22. File Type Usual extension Function Executable Exe, com, bin or none Ready to run machine language program Object obj, o Compiled, machine language, not linked Source code c, p, pas, f77, asm, a Source code in various languages Batch bat, sh Commands to the command interpreter Text txt, doc textual data,documents Word Wp, tex, rrf etc Various word processor Processor formats Library Lib, a Libraries of routines Print or view ps, dvi, gif ASCII or binary file in a format for printing or viewing Archive arc, zip, tar Related group of files for archiving or storage Fig : Common File Types http://raj-os.blogspot.in/ 22
- 23. File Type One major consideration in designing a file system, and the entire operating system, is whether the operating system should recognize and support file types http://raj-os.blogspot.in/ 23
- 24. File Type • If the operating system recognizes the type of a file • it can then operate on the file in reasonable ways • Ex : An attempt to print a binary-object form of a program file can be prevented http://raj-os.blogspot.in/ 24
- 25. File Type To implement file types, include the type as part of the file name For Ex : letters , documents http://raj-os.blogspot.in/ 25
- 26. File Type The file name is split into two parts - a name - an extension http://raj-os.blogspot.in/ 26
- 27. File Type • The file name is usually separated from the extension by a period ( dot ) character Ex : paycalc. cpp • The name can consists up to 8 characters followed by a period http://raj-os.blogspot.in/ 27
- 28. File Type The extension tells what the file type is • Extension can be up to 3 characters • System uses the extension to indicate the type of the file • Type of operations that can be done on that file For ex : .com , .exe & .bat extension are executable file http://raj-os.blogspot.in/ 28
- 29. Summary In this class, you have learnt - file concept - Understand file operations - Know various file types http://raj-os.blogspot.in/ 29