Commands.java

package com.cmdapp;

/**
 * Created with IntelliJ IDEA.
 * User: Andrew
 * Date: 10/1/13
 * Time: 5:02 PM
 * To change this template use File | Settings | File Templates.
 */
public enum Commands {
    EXIT, RECLIST, PWD, CD, LS, RM, LENGTH, TAIL, GREP;
}

Main.java

package com.cmdapp;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.*;
import java.util.concurrent.ArrayBlockingQueue;

public class Main {

    private static File location = new File(System.getProperty("user.dir"));

    public static void main(String[] args) throws IOException {
        Scanner cli = new Scanner(System.in);

        //noinspection InfiniteLoopStatement
        while (true) {
            String[] cmdLine = cli.nextLine().split(" ");

            List<String> params = new ArrayList<String>();
            Collections.addAll(params, cmdLine);

            Commands command = Commands.valueOf(cmdLine[0].toUpperCase());

            switch (command) {

                case EXIT:
                    exit();
                    break;
                case RECLIST:
                    reclist();
                    break;
                case PWD:
                    pwd();
                    break;
                case CD:
                    cd(cmdLine[1]);
                    break;
                case LS:
                    ls(params);
                    break;
                case RM:
                    rm(cmdLine[1]);
                    break;
                case LENGTH:
                    length(cmdLine[1]);
                    break;
                case TAIL:
                    tail(cmdLine[1], params);
                    break;
                case GREP:
                    grep(cmdLine[1], cmdLine[2]);
                    break;
            }

        }

    }

    private static void grep(String fileName, String regexp) throws IOException {
        File file = new File(fileName);
        if (file.exists()) {
            BufferedReader reader = new BufferedReader(new FileReader(file));

            String line;
            while ((line = reader.readLine()) != null) {
                if (line.matches(regexp)) System.out.println(line);
            }

            reader.close();
        } else System.out.println("Hiba");
    }

    private static void tail(String fileName, List<String> params) throws IOException {
        int n = 10;

        if (params.contains("-n"))
            n = Integer.parseInt(params.get(params.indexOf("-n") + 1));

        File file = new File(fileName);
        if (file.exists()) {
            BufferedReader reader = new BufferedReader(new FileReader(file));
            Queue<String> lines = new ArrayBlockingQueue<String>(n);

            String line;
            while ((line = reader.readLine()) != null) {
                if (!lines.offer(line))
                    lines.poll();
                lines.offer(line);
            }
            reader.close();

            for (String ln : lines) {
                System.out.println(ln);
            }
        } else System.out.println("Hiba");

    }

    private static void length(String fileName) {
        File file = new File(fileName);

        if (file.exists()) {
            System.out.println(file.getTotalSpace());
        } else System.out.println("Hiba");
    }

    private static void rm(String fileName) {
        File file = new File(fileName);

        if (!file.delete()) System.out.println("Hiba");

    }

    private static void ls(List<String> params) {
        File[] files = location.listFiles();
        for (File file : files != null ? files : new File[0]) {
            if (params.contains("-l"))
                System.out.println(((file.isDirectory()) ? "d" : "f") + " " + file.getName());
            else
                System.out.println(file.getName());
        }
    }

    private static void exit() {
        System.exit(0);
    }

    private static void reclist() {
        reclist(location, 1);
    }

    private static void reclist(File dir, int level) {
        char[] temp = new char[level];
        Arrays.fill(temp, '-');
        String levelPrefix = new String(temp);

        File[] files = dir.listFiles();
        for (File file : files != null ? files : new File[0]) {
            System.out.println(levelPrefix + file.getName());

            if (file.isDirectory()) reclist(file, level + 1);
        }
    }

    private static void pwd() {
        System.out.println(location.getAbsolutePath());
    }

    private static void cd(String dir) {
        if (dir.equals("..")) location = location.getParentFile();
        File[] files = location.listFiles();

        for (File file : files != null ? files : new File[0]) {
            if (file.getName().equals(dir)) {
                if (!file.isDirectory()) System.out.println("Not directory");
                location = file;
            }
        }
    }
}