1. CS-502 Fall 2006Project 1, Fork1 Programming Project 1 – Fork

2. CS-502 Fall 2006Project 1, Fork2 Programming Assignment 1.Write a command called doit to execute another command and print out statistics 2.Extend doit to become a basic shell that prompts for and executes commands 3.Extend your shell to shell2 to execute commands in the background

3. CS-502 Fall 2006Project 1, Fork3 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

4. CS-502 Fall 2006Project 1, Fork4 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()

5. CS-502 Fall 2006Project 1, Fork5 Part 1 (output) % doit cat /etc/motd /* print the current message of the day */ /* statistics about the cat command */

6. CS-502 Fall 2006Project 1, Fork6 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

7. CS-502 Fall 2006Project 1, Fork7 Part 2 output % shell ==>cat /etc/motd /* print the current message of the day */ /* statistics about the cat command */ ==>cd dir /* current directory is changed to dir */ ==>ls /* listing of files in current directory */ /* statistics about this ls command */ ==>exit %/* back to your previous Linux prompt */

8. CS-502 Fall 2006Project 1, Fork8 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

9. CS-502 Fall 2006Project 1, Fork9 Part 3 output % shell2 ==>numbercrunch & [1] 12345 /* indicate background task #1, process id */ ==>jobs [1] 12345 numbercrunch /* print process id and command name for tasks */ ==>ls /* listing of files in the current directory */ /* statistics about this ls command */ ==>cat /etc/motd [1] 12345 Completed /* statistics about background job */ /* print the current message of the day */ /* statistics about this cat command */ ==>exit %/* back to your previous Linux prompt */

10. CS-502 Fall 2006Project 1, Fork10 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

11. CS-502 Fall 2006Project 1, Fork11 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!)

12. CS-502 Fall 2006Project 1, Fork12 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

13. CS-502 Fall 2006Project 1, Fork13 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!