I'm trying to do an assignment to implement a unix shell and run commands using java. commands include read file, copy file, remove file and find substring in a file. I have managed to create the file and try out all commands individually but I've failed to run the threads. Below is a suggestion and code for individual commands:
Suggestion
The purpose of this assignment is to introduce you to Java programming. You are to implement a simple shell (command interpreter) that behaves similarly to the UNIX shell. When you type in a command (in response to its prompt), it will create a thread that will execute the command you entered.
Multiple commands can be chained together on a single line, The commands can either be separated by `&' (ampersand) or `;'.
The public static void main() procedure in your primary class will be quite simple. It will be an infinite loop that prints a prompt, reads a line (in other courses, a program with an infinite loop is considered a bad thing, but in Operating systems, it's the norm!), parses it (breaks it up into its constituent commands), either starts a new thread to handle each of the different commands if they are chained by `&', or starts the threads one by one if they are chained by ';', and then waits for all the threads to finish before printing the next prompt.
code:
//To create and write text to a file:
import java.lang.*;
import java.io.*;
public class Create
{
String command="";
BufferedReader br;
BufferedWriter out;
File file = new File("f1");
public void createFile()
{
try {
//File file = new File("f1");
// Create file if it does not exist
boolean success = file.createNewFile();
if (success)
{
writeFile();
}
else
{
System.out.println("file already exists");
}
} catch (IOException e) {}
}
public void writeFile()
{
try {
out = new BufferedWriter(new FileWriter(file));
out.write("You have passed \n");
out.write("The Exams");
out.close();
} catch (IOException e) {}
}
}
//To read file
import java.lang.*;
import java.io.*;
public class Read
{
BufferedReader br;
BufferedWriter out;
public void readFile()
{
try {
br = new BufferedReader(new FileReader("f1"));
String Str;
while ((Str = br.readLine()) != null)
{
System.out.println(Str);
}
br.close();
} catch (IOException e) {}
}
}
//To copy file
import java.lang.*;
import java.io.*;
public class Copy
{
public void copyFile()
{
try{
InputStream in = new FileInputStream("f1");
OutputStream out = new FileOutputStream("f2");
// Transfer bytes from in to out
byte[] buf = new byte[1024];
int length;
while ((length = in.read(buf)) > 0)
{
out.write(buf, 0, length);
}
in.close();
out.close();
System.out.println("File copied.");
}catch(IOException e) {}
}
}
//To remove file
import java.lang.*;
import java.io.*;
public class Remove
{
public void removeFile(File file)
{
boolean success = file.delete();
if (!success)
{
System.out.println("File not deleted");
}
}
}
//To check for substring
import java.lang.*;
import java.io.*;
public class Sub
{
BufferedReader br;
BufferedWriter out;
public void Search()
{
try {
br = new BufferedReader(new FileReader("f1"));
String Str;
while ((Str = br.readLine()) != null)
{
System.out.println(Str);
boolean found = true;
int index = Str.indexOf("have");
if(found)
{
System.out.println("Substring found");
System.out.println(br.readLine());
}
else
System.out.println(" ");
}
br.close();
} catch (IOException e) {}
}
}
Please help me to put all this together using threads. I've tried the main class but its really giving problems. Im looking forward to any one's reply.Thanks in advance.
Marked 
