Ch3 Exercises

Author: dalmia

3-Process Concept/exercises/3.10.c

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+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+
+#define SIZE 5
+
+int nums[SIZE] = {0,1,2,3,4};
+
+int main()
+{
+int i;
+pid_t pid;
+
+ pid = fork();
+ if(pid == 0){
+ for(i=0; i<SIZE; i++){
+ nums[i] *= -i;
+ printf("Child %d\n", nums[i]);
+ }
+ }
+ else if(pid > 0){
+ wait(NULL);
+ for (i = 0; i < SIZE; i++) {
+ printf("Parent %d\n", nums[i]);
+ }
+ }
+
+ return 0;
+}

3-Process Concept/exercises/3.12.c

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+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/types.h>
+
+int main()
+{
+pid_t pid,pid1;
+
+ pid = fork();
+ if(pid == 0){
+ pid1 = getpid();
+ printf("Child: pid = %d\n", pid1);
+
+ /* pass exit status */
+ exit(2);
+ }
+ else if(pid > 0){
+ // int status;
+ // pid = wait(&status);
+
+ /* get parent pid */
+ pid1 = getpid();
+ printf("Parent: pid = %d\n", pid1);
+
+ /* execute ps -l from the parent */
+ execlp("/bin/ps", "ps", "-l", NULL);
+
+ //execlp("/bin/kill", "kill", "-9", getppid(), NULL);
+ //printf("Exit status: status = %d\n", status);
+ }
+
+ return 0;
+}

3-Process Concept/exercises/3.14.c

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+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+
+int main()
+{
+int n;
+pid_t pid;
+
+ printf("Enter N:");
+ scanf("%d", &n);
+
+ /* create child process */
+ pid = fork();
+
+ if(pid == 0){ /* child process */
+ while(n > 1){
+ printf("%d, ", n);
+ if(n%2 == 0) n = n/2;
+ else n = 3*n + 1;
+ }
+ printf("%d\n", n);
+ }
+ else if(pid > 0){ /* parent process */
+ wait(NULL);
+ }
+
+ return 0;
+}

3-Process Concept/exercises/3.15.c

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+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+
+int main()
+{
+/* size (in bytes) of shared memory object */
+const int SIZE = 8192;
+/* name of the shared memory object */
+const char *name = "OS";
+
+/* shared memory file descriptor */
+int shm_fd;
+/* pointer to shared memory object */
+int *ptr;
+
+int n;
+pid_t pid;
+
+ printf("Enter N:");
+ scanf("%d", &n);
+
+ /* create the shared memory object */
+ shm_fd = shm_open(name, O_CREAT | O_RDWR, 0666);
+
+ /* create child process */
+ pid = fork();
+
+ if(pid == 0){ /* child process */
+ /* memory map the shared memory object */
+ ptr = (int *)mmap(0, SIZE, PROT_WRITE, MAP_SHARED, shm_fd, 0);
+ int i=0;
+ while(n > 1){
+ ptr[i++] = n;
+ if(n%2 == 0) n = n/2;
+ else n = 3*n + 1;
+ }
+ ptr[i] = n;
+ }
+ else if(pid > 0){ /* parent process */
+ wait(NULL);
+ /* memory map the shared memory object */
+ ptr = mmap(0, SIZE, PROT_READ, MAP_SHARED, shm_fd, 0);
+ int i=0;
+ while(ptr[i]!=1){
+ printf("%d,", ptr[i]);
+ i++;
+ }
+ printf("%d\n", ptr[i]);
+ }
+
+ return 0;
+}

3-Process Concept/exercises/3.5.c

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+#include <stdio.h>
+#include <unistd.h>
+
+int main()
+{
+pid_t pid;
+ int i;
+ int c=1;
+
+ for (i=0; i<2; i++){
+ c++;
+ pid=fork();
+ }
+ printf("PID %d\n", pid);
+ if(pid != 0){
+ wait(NULL);
+ printf("%d\n", c);
+ }
+ return 0;
+}

3-Process Concept/exercises/3.8.c

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+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+
+int main()
+{
+pid_t pid, pid1;
+
+ /* fork a child process */
+ pid = fork();
+
+ if(pid < 0){ /* error occured */
+ fprintf(stderr, "Fork failed");
+ return 1;
+ }
+ else if(pid == 0){ /* child process */
+ pid1 = getpid();
+ printf("child: pid = %d\n", pid);
+ printf("child: pid1 = %d\n", pid1);
+ }
+ else{ /* parent process */
+ pid1 = getpid();
+ printf("parent: pid = %d\n", pid);
+ printf("parent: pid1 = %d\n", pid1);
+ wait(NULL);
+ }
+
+ return 0;
+}

3-Process Concept/exercises/EchoClient.class

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+import java.net.*;
+import java.io.*;
+import java.util.*;
+
+public class EchoClient{
+ public static void main(String[] args){
+ try {
+ /* make connection to server socket */
+ Socket socket = new Socket("127.0.0.1", 6010);
+
+ /* setup reading and writing to the socket */
+ BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
+ PrintWriter writer = new PrintWriter(socket.getOutputStream(), true);
+
+ InputStream in = socket.getInputStream();
+ BufferedInputStream is = new BufferedInputStream(in);
+
+ /* byte array to store the input from BufferedInputStream */
+ byte[] contents = new byte[1024];
+ int len;
+ String input;
+
+ /* keep running until null encountered */
+ while( (input = reader.readLine()) != null){
+ /* write string to socket */
+ writer.write(input);
+ writer.flush();
+
+ /* read string from socket */
+ String line;
+ len = is.read(contents);
+ if(len == -1) break;
+ line = new String(contents, 0, len);
+ System.out.println(line);
+
+ /* exit on 'bye' */
+ if(line.toLowerCase().contains("bye")) break;
+ }
+
+ /* close the socket connection */
+ socket.close();
+ }catch(IOException ioe){
+ System.err.println(ioe);
+ }
+ }
+}

3-Process Concept/exercises/EchoClient.java

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+import java.net.*;
+import java.io.*;
+
+public class EchoServer{
+ public static void main(String[] args){
+ try{
+ ServerSocket sock = new ServerSocket(6010);
+
+ /* listen for connections */
+ while(true){
+ Socket client = sock.accept();
+ InputStream in = client.getInputStream();
+ BufferedInputStream is = new BufferedInputStream(in);
+ PrintWriter writer = new PrintWriter(client.getOutputStream(), true);
+
+ byte[] contents = new byte[1024];
+ int len;
+
+ while(true){
+ /* read input from socket */
+ len = is.read(contents);
+ 
+ /* echo back to client */
+ String line = new String(contents, 0, len);
+ writer.write("Server: " + line);
+ writer.flush();
+
+ if(line.toLowerCase().compareTo("bye")==0) break;
+ }
+
+ /* close the socket and resume listening for connections */
+ client.close();
+ }
+ }catch(IOException ioe){
+ System.err.println(ioe);
+ }
+ }
+}