CS-3013 . Operating Systems. Hugh C. Lauer. (Slides include materials from. Slides include materials from . Modern Operating Systems. , . 3. rd. ed. ., by Andrew . Tanenbaum. and from . Operating System Concepts. ID: 754398
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Presentations text content in Programming Project #1 Fork and Command Shell
Slide1
Programming Project #1Fork and Command Shell
CS-3013 Operating SystemsHugh C. Lauer (Slides include materials fromSlides include materials from Modern Operating Systems, 3rd ed., by Andrew Tanenbaum and from Operating System Concepts, 7th ed., by Silbershatz, Galvin, & Gagne)
CS-3013, C-Term 2012
Project #1, Fork and Command Shell
1
Slide2
Purpose
To practice using the fork and exec facilities of Unix/LinuxTo learn how to find and use on-line documentation about system calls and system facilities.man pagesTo become accustomed to speaking directly with the operating systemProject #1, Fork and Command Shell2CS-3013, C-Term 2012
Slide3
Programming Assignment
Build a command shell capable of running commands in the background:–Write a command called doit to execute another command and print out statisticsAdapt doit to become a basic shell that prompts for and executes commandsModify your shell to become shell2 to execute commands in the background
Project #1, Fork and Command Shell
3
CS-3013, C-Term 2012
Slide4
Part 1: doit
doit command:–Take another command line as argumentExecute that commandPrint out statistics about commandMust compile and execute on your virtual machineLikely to be compatible with most modern Linux systemsUseful system calls and functions:–fork(), execvp(), wait()getrusage(), gettimeofday()May not use system() system call
Project #1, Fork and Command Shell
4
CS-3013, C-Term 2012
Use
execvp
(), not
execve
()
Slide5
Part 1 (sample output
)% ./doit cat /etc/motd /* print the current message of the day */ /* statistics about the cat command */% ./doit
ls –l /
usr/src
/* list contents of the /
usr
/
src
directory */
/* statistics of the
ls
command */
% ./
doit
cp
–al /
usr
/
src
/linux-2.6.27.25-0.1
kernelSrc
/* output of the
cp
command (if any) */ /* statistics of the cp command */
Project #1, Fork and Command Shell
5
CS-3013, C-Term 2012
Slide6
doit Implementation Hint
Command line is already tokenized in argvStrip off the 0th element of argv vectorPass the remainder of argv to exec() for arguments of commandProject #1, Fork and Command Shell
6
CS-3013, C-Term 2012
Slide7
Questions?
CS-3013, C-Term 2012Project #1, Fork and Command Shell7
Slide8
Part 2: shell
Repeatedly prompt for command linesExecute each command and print out statistics, as in doitImplement special “built-in” commandsexitcd dir
Special conditionsInput from
stdinExit on end of fileComplain about illegal commands
Check for line length, number of arguments
Project #1, Fork and Command Shell
8
CS-3013, C-Term 2012
Slide9
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 –l /boot
/* listing of files in /boot directory */
/* statistics about this
ls
command */
==>exit
% /* back to your previous Linux prompt */
% shell < filename.txt
/* reads, echoes, and executes each command/*
/* statistics about each command */
/* exits after last command is completed */
Project #1, Fork and Command Shell
9
CS-3013, C-Term 2012
Slide10
shell Implementation Hints
Input command lineMay limit to 128 characters, 32 argumentsMust tokenize — use strtok() functionBuilt-in commands are not handled by fork and execMust be executed “in-line” in shell getrusage
() returns cumulative statisticsFor all children of this process
Must remember and subtract previous values to get statistics for most process most recently waited forProject #1, Fork and Command Shell
10
CS-3013, C-Term 2012
Slide11
Questions?
CS-3013, C-Term 2012Project #1, Fork and Command Shell11
Slide12
Part 3: Background Execution (
shell2)Modify shell to allow commands to execute in background, indicated by ‘&’ characterCauses shell to prompt for next command before previous command is completejobs built-in command lists background tasks in progressModified wait() callReturns immediately if nothing has terminated
Returns PID if any process has terminatedReport completion of command at next opportunity
I.e., the next time user types a command, or whenever wait() returns PID of the command
Project #1, Fork and Command Shell
12
CS-3013, C-Term 2012
Slide13
Part 3 output
% shell2==>make –j4 O=~/kernelDst &[1] 12345 /* indicate background task #1, process id */==>jobs[1] 12345 make /* 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 make Completed
/* statistics about background job */
/* print the current message of the day */
/* statistics about this cat command */
==>exit
% /* back to your previous Linux prompt */
Project #1, Fork and Command Shell
13
CS-3013, C-Term 2012
Slide14
shell2 Implementation Hints
Use wait3() to Wait for any processWait without blocking – WNOHANG optionGet usage information directlyAfter fork(), shell2 does
while (pid
= wait3(WNOHANG)) {print msg
& statistics of
pid
update list of outstanding tasks
}
if
(latest not background &&
latest not done)
wait3(
latest_pid
);
else get next command;
Project #1, Fork and Command Shell
14
CS-3013, C-Term 2012
Slide15
Work environment
Program in CEven though it could easily be done in C++Project can be carried out on any Linux systemE.g., your own or corporate environmentWe will grade it on openSUSE 11.4 I.e., your virtual machine environmentNote:Linux systems are often compatible with each otherHowever, not all C/C++ compilers and Linux kernels are alikeSome may produce or ignore compiler warningsYour virtual machine is the one that counts
Project #1, Fork and Command Shell
15
CS-3013, C-Term 2012
Slide16
Project submission
Due Sunday, January 22 @ 11:59 PMSubmit via web-based TurninProject name = Project 1Put your name at top of every file!(You would be surprised how many students forget!)Project #1, Fork and Command Shell16CS-3013, C-Term 2012
Slide17
Project Submission (continued
)Code of your solutionA single Makefilemake allmake doitmake shell
make shell2
make cleanTest cases for each part
Write-up explaining everything
Especially how
to keep
track of outstanding processes in
shell2
Zip
everything together
DO NOT
Put different parts of project in separate folders
Use different
makefiles
for different
parts of
project
Project #1, Fork and Command Shell
17
CS-3013, C-Term 2012
DO NOT create
.
rar
,
.
gz
,
.tar
, etc. files
Only
.zip
files are acceptable
Slide18
Grading
Ten point projectPart 1 – 2 pointsPart 2 – 3 pointsPart 3 – 4 pointsPoint allocation per partSee printed project descriptonWrite-up explaining what you did and your results1 pointMS Word or PDFNo credit for a part if it fails to buildProject #1, Fork and Command Shell18
CS-3013, C-Term 2012
Slide19
Not a team project!
Each student must submit own solutionEncouraged to discuss general approach, meaning of system calls, etc., with friendsEncouraged to seek help if puzzled by some concept, system call, etc.Distill all discussions into your own work!Project #1, Fork and Command Shell19CS-3013, C-Term 2012
Slide20
Questions?
CS-3013, C-Term 2012Project #1, Fork and Command Shell20
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DownloadNote - The PPT/PDF document "Programming Project #1 Fork and Command ..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Presentations text content in Programming Project #1 Fork and Command Shell
Programming Project #1Fork and Command Shell
CS-3013 Operating SystemsHugh C. Lauer (Slides include materials fromSlides include materials from Modern Operating Systems, 3rd ed., by Andrew Tanenbaum and from Operating System Concepts, 7th ed., by Silbershatz, Galvin, & Gagne)
CS-3013, C-Term 2012
Project #1, Fork and Command Shell
1
Slide2Purpose
To practice using the fork and exec facilities of Unix/LinuxTo learn how to find and use on-line documentation about system calls and system facilities.man pagesTo become accustomed to speaking directly with the operating systemProject #1, Fork and Command Shell2CS-3013, C-Term 2012
Slide3Programming Assignment
Build a command shell capable of running commands in the background:–Write a command called doit to execute another command and print out statisticsAdapt doit to become a basic shell that prompts for and executes commandsModify your shell to become shell2 to execute commands in the background
Project #1, Fork and Command Shell
3
CS-3013, C-Term 2012
Slide4Part 1: doit
doit command:–Take another command line as argumentExecute that commandPrint out statistics about commandMust compile and execute on your virtual machineLikely to be compatible with most modern Linux systemsUseful system calls and functions:–fork(), execvp(), wait()getrusage(), gettimeofday()May not use system() system call
Project #1, Fork and Command Shell
4
CS-3013, C-Term 2012
Use
execvp
(), not
execve
()
Slide5Part 1 (sample output
)% ./doit cat /etc/motd /* print the current message of the day */ /* statistics about the cat command */% ./doit
ls –l /
usr/src
/* list contents of the /
usr
/
src
directory */
/* statistics of the
ls
command */
% ./
doit
cp
–al /
usr
/
src
/linux-2.6.27.25-0.1
kernelSrc
/* output of the
cp
command (if any) */ /* statistics of the cp command */
Project #1, Fork and Command Shell
5
CS-3013, C-Term 2012
Slide6doit Implementation Hint
Command line is already tokenized in argvStrip off the 0th element of argv vectorPass the remainder of argv to exec() for arguments of commandProject #1, Fork and Command Shell
6
CS-3013, C-Term 2012
Slide7Questions?
CS-3013, C-Term 2012Project #1, Fork and Command Shell7
Slide8Part 2: shell
Repeatedly prompt for command linesExecute each command and print out statistics, as in doitImplement special “built-in” commandsexitcd dir
Special conditionsInput from
stdinExit on end of fileComplain about illegal commands
Check for line length, number of arguments
Project #1, Fork and Command Shell
8
CS-3013, C-Term 2012
Slide9Part 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 –l /boot
/* listing of files in /boot directory */
/* statistics about this
ls
command */
==>exit
% /* back to your previous Linux prompt */
% shell < filename.txt
/* reads, echoes, and executes each command/*
/* statistics about each command */
/* exits after last command is completed */
Project #1, Fork and Command Shell
9
CS-3013, C-Term 2012
Slide10shell Implementation Hints
Input command lineMay limit to 128 characters, 32 argumentsMust tokenize — use strtok() functionBuilt-in commands are not handled by fork and execMust be executed “in-line” in shell getrusage
() returns cumulative statisticsFor all children of this process
Must remember and subtract previous values to get statistics for most process most recently waited forProject #1, Fork and Command Shell
10
CS-3013, C-Term 2012
Slide11Questions?
CS-3013, C-Term 2012Project #1, Fork and Command Shell11
Slide12Part 3: Background Execution (
shell2)Modify shell to allow commands to execute in background, indicated by ‘&’ characterCauses shell to prompt for next command before previous command is completejobs built-in command lists background tasks in progressModified wait() callReturns immediately if nothing has terminated
Returns PID if any process has terminatedReport completion of command at next opportunity
I.e., the next time user types a command, or whenever wait() returns PID of the command
Project #1, Fork and Command Shell
12
CS-3013, C-Term 2012
Slide13Part 3 output
% shell2==>make –j4 O=~/kernelDst &[1] 12345 /* indicate background task #1, process id */==>jobs[1] 12345 make /* 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 make Completed
/* statistics about background job */
/* print the current message of the day */
/* statistics about this cat command */
==>exit
% /* back to your previous Linux prompt */
Project #1, Fork and Command Shell
13
CS-3013, C-Term 2012
Slide14shell2 Implementation Hints
Use wait3() to Wait for any processWait without blocking – WNOHANG optionGet usage information directlyAfter fork(), shell2 does
while (pid
= wait3(WNOHANG)) {print msg
& statistics of
pid
update list of outstanding tasks
}
if
(latest not background &&
latest not done)
wait3(
latest_pid
);
else get next command;
Project #1, Fork and Command Shell
14
CS-3013, C-Term 2012
Slide15Work environment
Program in CEven though it could easily be done in C++Project can be carried out on any Linux systemE.g., your own or corporate environmentWe will grade it on openSUSE 11.4 I.e., your virtual machine environmentNote:Linux systems are often compatible with each otherHowever, not all C/C++ compilers and Linux kernels are alikeSome may produce or ignore compiler warningsYour virtual machine is the one that counts
Project #1, Fork and Command Shell
15
CS-3013, C-Term 2012
Slide16Project submission
Due Sunday, January 22 @ 11:59 PMSubmit via web-based TurninProject name = Project 1Put your name at top of every file!(You would be surprised how many students forget!)Project #1, Fork and Command Shell16CS-3013, C-Term 2012
Slide17Project Submission (continued
)Code of your solutionA single Makefilemake allmake doitmake shell
make shell2
make cleanTest cases for each part
Write-up explaining everything
Especially how
to keep
track of outstanding processes in
shell2
Zip
everything together
DO NOT
Put different parts of project in separate folders
Use different
makefiles
for different
parts of
project
Project #1, Fork and Command Shell
17
CS-3013, C-Term 2012
DO NOT create
.
rar
,
.
gz
,
.tar
, etc. files
Only
.zip
files are acceptable
Slide18Grading
Ten point projectPart 1 – 2 pointsPart 2 – 3 pointsPart 3 – 4 pointsPoint allocation per partSee printed project descriptonWrite-up explaining what you did and your results1 pointMS Word or PDFNo credit for a part if it fails to buildProject #1, Fork and Command Shell18
CS-3013, C-Term 2012
Slide19Not a team project!
Each student must submit own solutionEncouraged to discuss general approach, meaning of system calls, etc., with friendsEncouraged to seek help if puzzled by some concept, system call, etc.Distill all discussions into your own work!Project #1, Fork and Command Shell19CS-3013, C-Term 2012
Slide20Questions?
CS-3013, C-Term 2012Project #1, Fork and Command Shell20