OS HW1solution

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HW 1-1


Finish “hw1_1.c” in order to design a C program to serve as a shell interface that accepts user commands then execute each command in a separate process.

UNIX shells typically allow the child process to run in the background or concurrently, so if a ampersand(&) at the end of the command means the parent and child processes will run concurrently.




You will use:

read(STDIN_FILENO, inputBuffer, MAX_LINE): read command line

fork(): create child process

execvp(char *command, char *params[]): execute system calls wait()

waitpid(pid)

…


HW 1-1


• Change directory

$cd your/folder/

    • Compile

$gcc -o shell hw1_1.c

• Execute

$./shell

• You need

    1. finish “hw1_1.c” as a shell interface.

    2. user can keep entering the command until he/she enters “exit”.(a command include the command itself and its parameters).

    3. if a user enter “&”, the shell should let child run in the background (means child and parent run concurrently).


Example


Show the content of hi.txt file 
Show the file in the directory

Show the date 

List all processes in current shell

Perform a full-format processes list 

Enter “exit” to finish shell 


Example


































Receive “-ael” as args and execute


Example













PID 15771&16230 becomes a zombie

(because ps –f & will let child process and parent process run concurrently, meaning that the parent process didn’t call “wait” for the child)


HW 1-2



Please draw the tree format according the code on the report(OS_document.docx).



You need to clarify which fork(fork0, fork1, fork2 or fork3)

the process been made by, for instance:



main

 fork0


process

fork1
fork2
fork2




…











HW 1-3


Write a program which uses fork() to produce the following tree format (namely, your code should have only 3 fork())


Main    fork3

fork1                  Child

Child    fork3

fork2                 Child
Child    fork3

Child



Time


HW 1-3


Output format








Main process 


Total 5 Children
The format & fork order
have to be same.
(Fork 1 2 3 3 3)



Hint:

Parent Process has to wait until Child Process finishes, then exit.

Use PID to identify parent and child.


Hint


Submission and Grade


Filename format please according : hw1-1.c, hw1-3.c (or .cpp), OS_report.docx. Put two *.c(*.cpp) files and a *.docx report into same compressed file named StudentID_hw1.zip (ex : 0000000_hw1.zip).

Deadline: 2018/10/14 (SUN) PM11:59

a. Total score: 100pts. COPY WILL GET A 0 POINT!

b. hw1-1 score: code 40pts, report Q1 10pts

c. hw1-2 score: report Q2 20pts

d. hw1-3 score: code 20pts, report Q3 10pts

e. Report: format is in OS_report.docx. YOU NEED TO FINISH EVERY PART OF REPORT TO GET SCORE!


Rules


        0. Use NCTU CS Workstation as your programming environment

    1. Use only C/C++, OTHER LANGUAGES WILL GET 0 POINT!

        2. Incorrect filename format will get -5 pts

        3. Incorrect output format will get -5 pts

        4. DELAYED SUBMISSION WILL GET 0 POINT!

*If you have any question, just send email to TAs.