static private int execute_command(string[] cmd)
        {

            switch (Interpreter.is_keyword(cmd[0])) //cmd0=first token
            {
                case Keyword.ls: return execute_ls(cmd);
                case Keyword.cd: return execute_cd(cmd);
                case Keyword.cat: return execute_cat(cmd);
                case Keyword.touch: return execute_touch(cmd);
                case Keyword.rm: return execute_rm(cmd);
                case Keyword.rmdir: return execute_rmdir(cmd);
                case Keyword.mkdir: return execute_mkdir(cmd);
                case Keyword.pwd: return execute_pwd(cmd);
                case Keyword.clear: return execute_clear(cmd);
                case Keyword.whoami: return execute_whoami(cmd);
                default: return execute_unknown_cmd(cmd);
            }
        }
        static public int execute_input(string[][] input)
        {
            int final = 0;
            for(int i =0; i<input.Length;i++)
            {
             final = execute_command(input[i]);
            }
            return final;
        }
        static private int show_content(string entry)
        {
            int final = 0;
            if(File.Exists(entry))
            {
                Console.WriteLine(entry);
                return 0;
            }
            else
            if (Directory.Exists(entry))
            {
                foreach (string s in Directory.GetFiles(entry))
                {
                    Console.WriteLine(s + "/");
                }
               final= 0;
            }
            else
            {
               final = 1;
            }
            return final;

        }
        static private int execute_ls(string[] cmd)
        {
            if (cmd.Length == 1)
            {
                return show_content("");
            }
            int final = 0;
            for (int i = 0; i < cmd.Length; i++)
            {
                final = show_content(cmd[i]);
            }
            return final;
        }
        static private int execute_cd(string[] cmd)
    {
        int result=0;
        if (Directory.Exists(path + "\\" + cmd[1]))
        {
            path += "\\" + cmd[1];
            result = 0;

        }
        if (File.Exists(path + "\\" + cmd[1]))
        {
            Console.WriteLine(cmd[1] + ":" + "Is not a directory");
            result = 1;

        }
        return result;
    }
        static private int execute_cat(string[] cmd)
        {

            int result = 0;
            for (int i = 0; i < cmd.Length; i++)
            {
                if (File.Exists(path + "\\" + cmd[i]))
                {
                    StreamReader streamreader = new StreamReader(path + "\\" + cmd[i]);
                    string a = streamreader.ReadToEnd();
                    Console.WriteLine(a);
                    streamreader.Close();
                    result = 0;
                }
                else
                {
                    Console.WriteLine("This is not a file");
                    result = 1;
                }
            }
            return result;
        }
        static private int execute_touch(string[] cmd)
        {
            int result = 0;
            for (int i = 1; i < cmd.Length; i++)
            {
                if (File.Exists(cmd[i]))
                {
                    Directory.SetLastAccessTime(cmd[i], DateTime.Now);
                    result = 0;
                }
                else if (Directory.Exists(cmd[i]))
                {
                    Directory.SetLastAccessTime(cmd[i], DateTime.Now);
                    result = 0;
                }
                else
                {
                    File.Create(cmd[i]);
                    result = 0;
                }
            }
            return result;
        }