CS519 01                                       Assignment 1
Due 06/11/2008

Part I: Report of Lecture Notes and Textbook studied on OS Concepts (Ch 1), Processes & Threads (Ch 2), and Deadlocks (Ch6)

Write a Microsoft report to summarize your self-study activities. The report must have the following.

1. The time and date of your study and the topics covered in each study session.

2. The summary of each topic studied.

3. Questions and answers in each study session (you may make up the questions or use the problems at the end of each chapter from the textbook.)

4. Conclusions of knowledge learned.

Email the report to the instructor on the due day.

Part II: OS Shell Project on cs1

Write a C/C++ program to simulate a simple shell (command interpreter) on CS1 UNIX (Solaris).
The program operations will be used to illustrate the process creation, synchronization, and execution using FORK, WAIT, and SYSTEM Unix commands The shell should be called SSH (short for Simple SHell) and its initial prompt should be "> ".

1. SSH should first prompt user for the login name and password. The list of login names and passwords should be stored in a table.
SSH will continue with a new "ssh> " prompt if the login is successfully.

- The password stored in the table must be encrypted.
- You may use any available encryption function or design your own encryption function to encrypt the password.

2. SSH should then read the command and parameters entered by the user,
where the syntax of commands is:

command [parameter | [parameter]*] /* [] means optional, | means or, * means 0 or more */

SSH will analyze the command. If the command is one of the following commands
supported by the SSH, it forks a new process to execute the command.
Otherwise it prints the error message.

The SSH commands should be initially stored in an external file and read into a command array when SSH starts.

The initial set of 7 commands supported by the SSH are:

newpwd /* Change the password – Write your own SSH function to change the password */
copy fileName1 fileName2 [fileName3]
/* Copies the contents of fileName1 and fileName2 onto the screen
or copy fileName1 and fileName2 to fileName3 if fileName3 is provided. You may use the UNIX command “cat” or “cp” to copy the files*/
edit [subdirName].fileName
/* edit an existed file in the current directory or in a subdirectory if the subdirName is provided. You may use the UNIX command “vi” or “pico” to edit the file */
display [loginName] /* display the status of all current processes, or display the processes belong to the user
if the loginName is provided. You may use the UNIX command “ps –ef | grep loginName” to display processes status */
search word fileName
/* search a word in a file.
Print the lines where the word is found. You may use the UNIX command “grep” to search a word in the file */
history /* list of all previous commands executed - Write your own SSH function to list the history */
logout /* the SSH should exit the shell after other commands are completed. */

(Extra credit: Program the upper arrow key to list the previous command executed.)

(You may learn UNIX commands either on the internet or use “man” UNIX command on cs1 to list the manual page, for example use “man ls” to list the manual page of ls command.)

3) SSH should fork a child process to execute the command. The parent process will wait for the
termination of the child process before go back to the "ssh>" prompt if the command is in a foreground process, otherwise it simply go back to the "ssh>" prompt if the command is in a background process.
- The command should be executed as a background process if a “&” sign is followed with the command.

4) The main() function should follow the following program structure.

build_command(); /* read in the commands into a table */

user_login(); /* Authenticate the user */

while (i < N) { /* repeat maximum N times */

type_prompt( ); /* display prompt */

n=read_command (command, parameters, background) /* input from terminal */

if (n>0) { /* valid command */

if (pid = fork() != 0) { /* Parent code */

if !(background) {

pid = wait( &status); /* wait for child to exit */

if (status == LOGOUTCODE) exit(0);

}

} else { /* Child code */

exec_command (command, parameters); /* execute command */

exit(0);

}

} else { cout << “Invalide command, try again\n”; }

}

Testing Requirements:
Test every command supported by the SSH in a foreground process. Test one command in a background process.

Assignment Hand-in Policies:
   1) Email me a Microsoft word report that describe your program structure and operations.
       Attach the programs source code and run results (screen shots) on your report.
   2) Good program modular design, data structures, algorithms, and internal documentation are part of the grade.