operating system program

8/2/2019 Operating System Program..

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solution with lockfile:

#!/bin/bash

if [ -e number.txt ]; thenecho "File exists"

elseecho "File does not exists. Create file

now."echo 1 > number.txt

fi

lockfile script.lock

a=$(/usr/bin/tail -n 1 number.txt)

if [ $a -gt 1 ]; thena=$(/usr/bin/tail -n 1 number.txt)

/usr/bin/expr $a - 1 >> number.txtfi

if [ $a -lt 2 ]; thena=$(/usr/bin/tail -n 1 number.txt)/usr/bin/expr $a + 1 >> number.txt

fi

rm -f script.lock


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The program in Listing 8.2 opens a file for writing whose name isprovided on the command line, and then places a write lock on it.The program waits for the user to hit Enter and then unlocks andcloses the file.

Listing 8.2 (lock-file.c) Create a Write Lock withfcntl

#include

#include

#include

#include

int main (int argc, char* argv[])
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{

char* file = argv[1];

int fd;

struct flock lock;

printf ("opening %s\n", file);

/* Open a file descriptor to the file. */

fd = open (file, O_WRONLY);

printf ("locking\n");

/* Initialize the flock structure. */

memset (&lock, 0, sizeof(lock));

lock.l_type = F_WRLCK;

/* Place a write lock on the file. */

fcntl (fd, F_SETLKW, &lock);

printf ("locked; hit Enter to unlock... ");

/* Wait for the user to hit Enter. */

getchar ();

printf ("unlocking\n");

/* Release the lock. */

lock.l_type = F_UNLCK;

fcntl (fd, F_SETLKW, &lock);

close (fd);


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return 0;

}

Compile and run the program on a test filesay, /tmp/test-

file

like this:

% cc -o lock-file lock-file.c

% touch /tmp/test-file

% ./lock-file /tmp/test-file

opening /tmp/test-file

locking

locked; hit Enter to unlock...

Now, in another window, try running it again on the same file.

% ./lock-file /tmp/test-file

opening /tmp/test-file

locking

Note that the second instance is blocked while attempting to lock

the file. Go back to the first window and press Enter:

unlocking

The program running in the second window immediately acquiresthe lock.

If you prefer fcntl not to block if the call cannot get the lock you

requested, use F_SETLK instead of F_SETLKW. If the lock cannot

be acquired, fcntl returns

1 immediately.

Linux provides another implementation of file locking withthe flock call. The fcntl version has a major advantage: Itworks with files on NFS3file systems (as long as the NFS serveris reasonably recent and correctly configured). So, if you have
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access to two machines that both mount the same file system viaNFS, you can repeat the previous example using two differentmachines. Run lock-file on one machine, specifying a file onan NFS file system, and then run it again on another machine,

specifying the same file. NFS wakes up the second programwhen the lock is released by the first program.

//Shared Memory Segment

Program 1:

#include #include #include

#include #include #define SHMSZ 27

main(){

char c;int semid,retval;struct sembuf sop,sop1;int shmid;key_t key;

char *shm, *s;


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key = 5678;semid=semget(20,1,0666|IPC_CREAT);semctl(semid,0,SETVAL,1);if ((shmid = shmget(key, SHMSZ, IPC_CREAT | 0666)) avail[j])

waitcheck=1;

}if (violationcheck==1)printf(\n\n\t The Process Exceeds its Max Need:

Terminated);else if(waitcheck==1)printf(\n\n\t Lack of Resourcess : Process State Wait);

else

{for(j=0;j


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}ch1=safeseq();if(ch1==0){

printf(\n\n\t Granting leads to Unsafe state : );

printf(\n\n\t Request Denied );

for(j=0;j


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printf( %d ,p[i].max[j]);printf(\t);for(j=0;j


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for(k=0;k


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* This module can be compiled using 'cc

bankersalgorithm.c' and executed using './a.out'

//inculsion.

#include

//macro definition

#define cls() printf("\033[H\033[J")

#define delay() for(h=0;h


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//inserting the assumed values.

available_res[0]=3; available_res[1]=1; available_res[2]=1;

available_res[3]=2;

cur_allocated_res[0][0]=1;cur_allocated_res[0][1]=2;cur_allo

cated_res[0][2]=2;cur_allocated_res[0][3]=1;





max_req_res[0][0]=3; max_req_res[0][1]=3;


max_req_res[1][0]=1; max_req_res[1][1]=2;max_req_res[1][2]=3; max_req_res[1][3]=4;



//assuming the request.

req_queue[0]=0;req_queue[1]=1;req_queue[2]=2;req_queu

e[3]=0;req_queue[4]=2;req_queue[5]=1;

req_type[0]=0;req_type[1]=0;req_type[2]=0;req_type[3]=1;re

q_type[4]=1;req_type[5]=1;display();

i=0;j=0;

while(i


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getrequest(req_queue[i]);

printf("\nChecking safe state.....\n");

delay();

if(issafe())

{

printf("\nSafe state detected....\nAllocating resources

.......\n");

allocate(req_queue[i]);

}

else

{

printf("\nUnsafe state detected....\nInserting the processinto waiting queue.\n");

j=j+1;

wait_queue[j]=req_queue[i];

}

}

else

{

printf("for resource deallocation.\n");deallocate(req_queue[i]);

printf("\nDeallocation done.\n\n%d processes in the wait

queue\n",j);

if(j>0)

{

while(j>0)

{

printf("\nConsidering the waiting queue processP%d\n",wait_queue[j]+1);

getrequest(wait_queue[j]);

printf("\nChecking safe state.\n");

delay();

if(issafe())


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{

printf("\nSafe state detected\nResources allocated\n");

allocate(wait_queue[j]);

j--;

}

else

{

break;

}

}

}

}delay();

i++;

}

}

void getrequest(int i)

{

int j;

for(j=0;j


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return 1;

}

void allocate(int i)

{

int j;

for(j=0;j


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printf("\n\n\t\t\t\tDETAILS.");

printf("\n\t\t\t\t________");

printf("\n\n\t\tNO OF PROCESSES:\tP1 P2 P3");

printf("\n\n\t\tNO OF RESOURCES:\tA B C D");

printf("\n\n\t\t\tThe status .............");

printf("\nThe available resources are.\n\t\tA B C D\n\t\t");

for(i=0;i


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fgets(a,2,stdin);

}

Program for FIFO page replacement algorithm

#include#includeint fr[3];void main(){

void display();int i,j,page[12]={2,3,2,1,5,2,4,5,3,2,5,2};int flag1=0,flag2=0,pf=0,frsize=3,top=0;clrscr();for(i=0;i


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{flag1=1;flag2=1;break;}}if(flag1==0){for(i=0;i=frsize)top=0;}display();}printf("Number of page faults : %d ",pf);

getch();}void display(){int i;printf("\n");


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for(i=0;i


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6789

1011121314151617

1819202122232425

262728293031323334

353637383940

void display();intp[12]={2,3,2,1,5,2,4,5,3,2,5,2},i,j,fs[3];int index,k,l,flag1=0,flag2=0,pf=0,frsize=3;clrscr();for(i=0;i


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414243444546474849505152

5354555657585960

616263646566676869

for(i=0;i


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2 3 12 5 12 5 12 5 42 5 43 5 43 5 23 5 23 5 2no of page faults : 4

Sockets Example

Introduct

ion

JAVA

Menu

Sockets

Text

Files

CSSCSS

tutorial

LINUX

Comman

This example introduces you to Java socket programming.

The server listens for a connection. When a connection is

established by a client. The client can send data. In the

current example the client sends the message "Hi my

server". To terminate the connection, the client sends the

message "bye". Then the server sends the message "bye"

too. Finally the connection is ended and the server waits for

an other connection. The two programs should be runned in

the same machine. however if you want to run them in two

different machines, you may simply change the adress

"localhost" by the IP adress of the machine where you will

run the server.

The server

import java.io.*;import java.net.*;
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ds public class Provider{ServerSocket providerSocket;Socket connection = null;ObjectOutputStream out;

ObjectInputStream in;String message;Provider(){}void run(){

try{//1. creating a server

socket

providerSocket = newServerSocket(2004, 10);//2. Wait for connection

System.out.println("Waiting forconnection");

connection =providerSocket.accept();

System.out.println("Connectionreceived from " +connection.getInetAddress().getHostName());

//3. get Input and Outputstreams

out = newObjectOutputStream(connection.getOutputS

tream());out.flush();in = new

ObjectInputStream(connection.getInputStream());

sendMessage("Connection
http://zerioh.tripod.com/ressources/lincommands.htmlhttp://zerioh.tripod.com/ressources/lincommands.htmlhttp://zerioh.tripod.com/ressources/lincommands.html


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successful");//4. The two parts

communicate via the input and outputstreams

do{try{

message =(String)in.readObject();

System.out.println("client>" +message);

if

(message.equals("bye"))

sendMessage("bye");}

catch(ClassNotFoundExceptionclassnot){

System.err.println("Data received

in unknown format");}

}while(!message.equals("bye"));}catch(IOException

ioException){

ioException.printStackTrace();}finally{

//4: Closing connectiontry{

in.close();


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out.close();

providerSocket.close();}

catch(IOExceptionioException){

ioException.printStackTrace();}

}}void sendMessage(String msg)

{ try{out.writeObject(msg);out.flush();

System.out.println("server>" +msg);

}catch(IOException

ioException){


}public static void main(String

args[]){

Provider server = newProvider();

while(true){server.run();

}}


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}

The client

import java.io.*;import java.net.*;public class Requester{

Socket requestSocket;ObjectOutputStream out;ObjectInputStream in;String message;Requester(){}

void run(){

try{//1. creating a socket to

connect to the serverrequestSocket = new

Socket("localhost", 2004);

System.out.println("Connected tolocalhost in port 2004");//2. get Input and Output

streamsout = new

ObjectOutputStream(requestSocket.getOutputStream());

out.flush();in = new

ObjectInputStream(requestSocket.getInputStream());

//3: Communicating withthe server

do{try{


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message =(String)in.readObject();

System.out.println("server>" +

message);sendMessage("Hi

my server");message = "bye";

sendMessage(message);}

catch(ClassNotFoundExceptionclassNot){

System.err.println("data receivedin unknown format");

}

}while(!message.equals("bye"));}

catch(UnknownHostExceptionunknownHost){

System.err.println("Youare trying to connect to an unknownhost!");

}catch(IOException

ioException){

ioException.printStackTrace();}finally{

//4: Closing connectiontry{


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in.close();out.close();

requestSocket.close();

}catch(IOException

ioException){


}}

void sendMessage(String msg){try{

out.writeObject(msg);out.flush();

System.out.println("client>" +msg);

}

catch(IOExceptionioException){


}public static void main(String

args[])

{Requester client = new

Requester();client.run();

}}


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Servlets - Session Management ExampleAfter user authentication, start a session. Display "Welcome[username]" as the response along with a link that hits anotherServlet. From this other servlet, send the response "You are[username]" by retrieving the username information from thesession as an attribute.

1) Servlet 1: Code here -http://www.javaissues.com/2011/02/servlets-handling-get-request.html

2) Servlet 2 - PostServlet.java

package info.icontraining.servlets;

import java.io.IOException;import java.io.PrintWriter;

import javax.servlet.http.*;

public class PostServlet extends HttpServlet {
http://www.javaissues.com/2011/02/servlets-handling-get-request.htmlhttp://www.javaissues.com/2011/02/servlets-handling-get-request.htmlhttp://www.javaissues.com/2011/02/servlets-handling-get-request.htmlhttp://www.javaissues.com/2011/02/servlets-handling-get-request.htmlhttp://www.javaissues.com/2011/02/servlets-handling-get-request.htmlhttp://www.javaissues.com/2011/02/servlets-handling-get-request.html


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public void doPost(HttpServletRequest

request, HttpServletResponse response) throwsIOException {

PrintWriter out = response.getWriter();

String username =request.getParameter("user");

String passwd =request.getParameter("pass");

out.println("");out.println("Post Servlet

Example");out.println("");

if (username.equals("dinesh") &&passwd.equals("dinesh")) {

out.println("Welcome " + username+"!");

HttpSession session =

request.getSession();

session.setAttribute("username",username);out.println("Click here");

} else {out.println("Invalid username/passwd.

Go back and try again.");}

out.println("");out.close();

}


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}

3) Servlet 3 - LinkedServlet.java

package info.icontraining.servlets;

import java.io.IOException;import java.io.PrintWriter;

import javax.servlet.http.*;

public class LinkedServlet extends HttpServlet {

public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException{

PrintWriter out = response.getWriter();

out.println("");out.println("Session

Management Example");out.println("");

HttpSession session =request.getSession();

String username =(String)session.getAttribute("username");

out.println("You are " + username +"!");

out.println("");out.close();

}}


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web.xml configuration for Servlets 2 & 3 (for configuration ofServlet 1, go to link specified above)

postServletinfo.icontraining.servlets.PostServlet

postServlet/formurl

linkedServletinfo.icontraining.servlets.LinkedServlet

linkedServlet/linkedServlet

operating system program

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