Initial commit

Problem 3.16/SocketClient.java

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+import java.net.*;
+import java.io.*;
+
+public class SocketClient {
+    public static void main(String[] args) {
+        try {
+            // make connection to server socket
+            Socket sock = new Socket("127.0.0.1", 6017);
+            InputStream in = sock.getInputStream();
+            BufferedReader bin = new BufferedReader(new InputStreamReader(in));
+
+            // get a qoute from the socket
+            String line;
+            while ( (line = bin.readLine()) != null)
+                System.out.println(line);
+
+            // close the socket connection
+            sock.close();
+        }
+        catch (IOException ioe) {
+            System.err.println(ioe);
+        }
+    }
+}

Problem 3.16/SocketServer.java

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+import java.net.*;
+import java.io.*;
+
+public class SocketServer {
+    public static String[] qoutes = {
+        "Don't cry because it's over, smile because it happened.",
+        "Be yourself; everyone else is already taken.",
+        "Two things are infinite: the universe and human stupidity; and I'm not sure about the universe.",
+        "So many books, so little time.",
+        "Be who you are and say what you feel, because those who mind don't matter, and those who matter don't mind."
+    };
+
+    public static void main(String[] args) {
+        try {
+            int i = 0;
+            ServerSocket sock = new ServerSocket(6017);
+
+            // Listening for connections
+            while (true) {
+                Socket client = sock.accept();
+                PrintWriter pout = new PrintWriter(client.getOutputStream(), true);
+
+                // write a qoute to the socket
+                pout.println(qoutes[i]);
+                i = (i + 1) % qoutes.length;
+
+                // close the socket and resume
+                // listening for connections
+                client.close();
+            }
+        }
+        catch (IOException ioe) {
+            System.err.println(ioe);
+        }
+    }
+}

Problem 3.18/SocketClient.java

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+import java.net.*;
+import java.io.*;
+import java.util.Scanner;
+
+public class SocketClient {
+    public static void main(String[] args) {
+        Socket sock = null;
+        Scanner scanner = null;
+        try {
+            sock = new Socket("127.0.0.1", 6017);
+            scanner = new Scanner(System.in);
+            DataOutputStream outputStream = new DataOutputStream(sock.getOutputStream());
+            DataInputStream inputStream = new DataInputStream(sock.getInputStream());
+            while (true) {
+                try {
+                    System.out.print("Input: ");
+                    String message = scanner.nextLine();
+                    outputStream.writeUTF(message);
+                    System.out.println("Echo: " + inputStream.readUTF());
+                } catch (IOException e) {
+                    System.err.println(e);
+                }
+            }
+        }
+        catch (IOException ioe) {
+            System.err.println(ioe);
+        }
+        finally {
+            try {
+                scanner.close();
+                sock.close();
+            } catch (IOException e) {}
+        }
+    }
+}

Problem 3.18/SocketServer.java

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+import java.net.*;
+import java.io.*;
+
+public class SocketServer {
+    public static void main(String[] args) {
+        ServerSocket sock = null;
+        Socket client = null;
+        try {
+            sock = new ServerSocket(6017);
+            client = sock.accept();
+            DataInputStream inputStream = new DataInputStream(client.getInputStream());
+            DataOutputStream outputStream = new DataOutputStream(client.getOutputStream());
+            while (true) {
+                try {
+                    String message = inputStream.readUTF();
+                    System.out.println("Client: " + message);
+                    outputStream.writeUTF(message);
+                } catch (IOException e) {
+                    if (e.getMessage().equals("null")) {
+                        break;
+                    }
+                }
+            }
+            inputStream.close();
+            outputStream.close();
+            client.close();
+            sock.close();
+        }
+        catch (IOException ioe) {
+            try {
+                sock.close();
+                client.close();
+            } catch (IOException e) {}
+            System.err.println(ioe);
+        }
+    }
+}

Problem 3.20/main.c

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+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <fcntl.h>
+#define SIZE 65536
+
+int main(int argc, char *argv[]) {
+    int pipefd[2];          // pipefd[0] represents input stream id, pipefd[1] represents output stream id.
+    char buffer[SIZE];      // The buffer of main process.
+    char childBuffer[SIZE]; // The buffer of sub-process.
+
+    // If the number of arguments is not correct.
+    if (argc != 3) {
+        perror("Main: main [target] [destination].\n");
+        return 1;
+    }
+
+    char *srcFile = argv[1]; // Source
+    char *dstFile = argv[2]; // Destination
+
+    // Building a pipe. If the returned integer is less than 0,
+    if (pipe(pipefd) < 0) {
+        printf("An error occured when createing the pipe: %s\n", strerror(errno));
+        return 1;
+    }
+    
+    pid_t pid = fork(); // Create a sub-process.
+
+    if (pid == 0) {         // pid == 0 represents it's a sub-process.
+        close(pipefd[1]);   // Close pipefd[1]
+        ssize_t file_size = read(pipefd[0], childBuffer, sizeof(childBuffer));  // Get the size of child
+        close(pipefd[0]);                                       // Close pipefd[0] since it is unable to use.
+        int dst_file_fd = open(dstFile, O_CREAT | O_WRONLY);    //  Read a file in writeonly mode. If the file does not exit, create a new one.
+        write(dst_file_fd, childBuffer, file_size);             // Write data from buffer into fd.
+        close(dst_file_fd);                                     // Close file
+    }
+    else if (pid > 0) { // pid > 0 represents it's a main process.
+        close(pipefd[0]);                                                   // Close pipefd[0]
+        int target_file_fd = open(srcFile, O_RDONLY);                       // Open a file in readonly mode.
+        ssize_t file_size = read(target_file_fd, buffer, sizeof(buffer));   // Get size of the file
+        write(pipefd[1], buffer, file_size);                                // Write data from buffer into pipefd[1]
+        close(pipefd[1]);                                                   // Close pipefd[1]
+        close(target_file_fd);                                              // Close file
+    }
+    else { // When error occur
+        printf("An error occured when forking child process. %s\n", strerror(errno));
+        return 1;
+    }
+    return 0;
+}

README.md

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+Operating System Second Assignment
+===
+
+Programming Problems 3.16, 3.18, 3.20 對應至目錄 `Problem 3.16`, `Problem 3.18` 與 `Problem 3.20` 上