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File System Abstraction - Advanced Unix Programming - Lecture Slides, Slides of Computer Programming

University of LucknowComputer Programming

Some concept of Advanced Unix Programming are Address Structure, Basic Thread Functions, Client-Server Design, Network Programming, Signals and Thread, Thread-Specific Data, Unix File System, Reliable Communication. Main points of this lecture are: File System Abstraction, Unix File System, Directories, File Descriptors, Programming, Unlink, Variable Argument List, Process Management, Redirection, Named and Unnamed Pipes

Typology: Slides

2012/2013

Uploaded on 04/29/2013

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Week 3 Topics
•UNIX file system
–File system abstraction
–Directories
–File descriptors
•Unix API Programming Examples and Techniques
–Example with direct IO
•open, close, fdopen, lseek, unlink
–Variable argument list
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Download File System Abstraction - Advanced Unix Programming - Lecture Slides and more Slides Computer Programming in PDF only on Docsity!

Week 3 Topics

  • UNIX file system
    • File system abstraction
    • Directories
    • File descriptors
  • Unix API Programming Examples and Techniques
    • Example with direct IO
      • open, close, fdopen, lseek, unlink
    • Variable argument list

Week 3 Topics ... continued

  • File I/O
    • File descriptors
      • open, creat, close, dup, dup
    • I/O redirection
  • Process management
    • fork, exit, wait, waitpid, execv
  • Pipes
    • Named and unnamed pipes
    • Implementing pipe in a shell

File descriptors

  • Implication of the file descriptor/open file

descriptions/inode table organization in UNIX

  • open and creat
    • search for the first empty slot in the process file descriptor table
    • allocate an open file description in the file table, which has a pointer to the inode table
    • See example1.c
  • dup and dup
    • Duplicate the file descriptor in the process file descriptor table
    • See example1b.c
    • Where is the current file position stored?

I/O redirection

  • All UNIX processes have three predefined files

open

  • stdin -- STDIN_FILENO (0)
  • stdout -- STDOUT_FILENO (1)
  • stderr -- STDERR_FILENO (2)
  • We can redirect the I/O by manipulating these file

descriptors

  • See example2.c and example3.c

fork()

• fork()

  • Create a new process by duplicating the

context of the calling process

  • The calling process is called the parent , and the

new process the child

  • The return value of fork() distinguishes the two

processes

  • See example4.c and example5.c

exit() and wait()

  • exit (int status)
    • Clean up the process (for example, close all files)
    • Tell its parent that it is dying (SIGCHLD)
    • Tell child processes that it is dying (SIGHUP)
    • status can be accessed by the parent
  • wait, waitpid
    • Wait for a child process to die
      • pid_t wait(int *stat_loc)
    • Suspend the calling process to wait for a child process to die - Return the pid and status of the child process
  • See example6.c