Files and File Management

• File management system provides services to hide the specifics of tape and disk
• Invoked by system calls
• Files are grouped together by a directory
  • Organized as a hierarchical tree
  • Root directory
  • Files specified by path name
  • Path name separator (/ in Unix, \ in DOS)
  • Working directory
• Protection of files
  • Based on a 9-bit code in Unix -- rwx bits
• File descriptor or handle
  • A small integer to identify a file in subsequent operations
  • A denial of access indicated by an error code
  • 0 Standard input
  • 1 Standard output
  • 2 Standard error
• I/O devices treated as special files
  • b Block special files
  • c Character special files
• Pipes
  • A pseudo file to connect two processes
• Unix file system