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/**Perhaps the easiest technique for implementing a shell interface is to have the program first read what the user enters on the command line (here, cat Prog.java) and then have the program create a separate external process that performs the command. You can create the separate process using the code provided below:**/
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import java.io.*;
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public class AProcess
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{
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public static void main(String[] args) throws IOException {
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if (args.length != 1) {
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System.err.println("Usage: java OSProcess <command>");
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System.exit(0);
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}
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// args[0] is the command
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ProcessBuilder pb = new ProcessBuilder(args[0]);
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Process process = pb.start();
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// obtain the input and output streams
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InputStream is = process.getInputStream();
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InputStreamReader isr = new InputStreamReader(is);
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BufferedReader br = new BufferedReader(isr);
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String line;
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while ( (line = br.readLine()) != null)
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System.out.println(line);
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br.close();
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}
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}
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/**The following code contains the basic operations of a command-line shell. The main() method presents the prompt ‘prompt>’ and waits to read input from the user. The program is terminated when the user enters <Control><C>.**/
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import java.io.*;
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public class ABasicShell
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{
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public static void main(String[] args) throws java.io.IOException {
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String commandLine;
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BufferedReader console = new BufferedReader(new InputStreamReader(System.in));
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// we break out with <control><C>
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while (true) {
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// read what they entered
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System.out.print("prompt>");
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commandLine = console.readLine();
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// if they entered a return, just loop again
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if (commandLine.equals(""))
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continue;
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/**
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The basic steps are:
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(1) parse the input to obtain the command
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and any parameters
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(2) create a ProcessBuilder object
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(3) start the process
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(4) obtain the output stream
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(5) output the contents returned by the command
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*/
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}
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}
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}
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