Programming Project 1 Fork

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Programming Project 1 Fork
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Programming Assignment

• Write a command called doit to execute another
  command and print out statistics
• Extend doit to become a basic shell that prompts
  for and executes commands
• Extend your shell to shell2 to execute commands
  in the background

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Purpose

• To practice using the fork and exec facilities of
  Unix/Linux
• To learn how to find and use on-line
  documentation about system calls and system
  facilities.
• man pages
• To be accustomed to speaking directly with the
  operating system

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Part 1 doit

• doit command
• Take another command line as argument
• Execute that command
• Print out statistics about command
• Must execute on a CCC or CS Linux system
• May not use system() system call
• Helpful hints
• fork(), execvp(), wait()
• getrusage(), gettimeofday()

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Part 1 (output)

• doit cat /etc/motd
• / print the current message of the day /
• / statistics about the cat command /

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Part 2 shell

• Repeatedly prompt for command lines
• Execute each command and print out statistics, as
  in doit
• Implement special built-in commands
• exit
• cd dir
• Special conditions
• Input from stdin
• Exit on end of file
• Complain about illegal commands
• Check for line length, number of arguments

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Part 2 output

• shell
• gtcat /etc/motd
• / print the current message of the day /
• / statistics about the cat command /
• gtcd dir
• / current directory is changed to dir /
• gtls
• / listing of files in current directory /
• / statistics about this ls command /
• gtexit
• / back to your previous Linux prompt /

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Part 3 Background execution (shell2)

• Modify shell to support execute commands in
  background, indicated by character
• Causes shell to prompt for next command before
  previous command is complete
• jobs built-in command lists background tasks in
  progress
• Report completion at next opportunity
• E.g., the next time user types a command, but
  before executing that command

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Part 3 output

• shell2
• gtnumbercrunch
• 1 12345 / indicate background task 1,
  process id /
• gtjobs
• 1 12345 numbercrunch
• / print process id and command name for tasks
  /
• gtls
• / listing of files in the current directory /
• / statistics about this ls command /
• gtcat /etc/motd
• 1 12345 Completed lt background job command gt
• / statistics about background job /
• / print the current message of the day /
• / statistics about this cat command /
• gtexit
• / back to your previous Linux prompt /

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Work environment

• You may do this work on
• CCC machine
• CS machine
• Your virtual machine (if you have set it up
  already)
• You may use C or C
• Note
• CCC and CS do not use same version of Linux
  kernel or C/C compiler
• Your virtual machine uses the latest version

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Project submission

• Due Monday, September 25, at start of class
• Submit via turnin
• command /cs/bin/turnin on CCC machines
• classname cs502
• assignment project1
• Put your name at top of every file!
• (You would be surprised how many students forget!)

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Project Submission (continued)

• Code of your solution
• Makefile to build all programs
• One or more test cases
• Write-up explaining everything
• DO NOT
• Put different parts of projects in folders
• Create different Makefiles for different parts

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Not a team project!

• Each student must submit own solution
• Encouraged to discuss general approach, meaning
  of system calls, etc., with friends
• Encouraged to seek help if puzzled by some
  concept, system call, etc.
• Distill all discussions into your own work!