dsl

#!/usr/bin/ruby

class BasicShell

  attr_reader :env

  def initialize
    @env={ }
    @env["prompt"] = "b> "
  end

  def ls p="*"
    puts Dir[p]
  end

  def cd d
    Dir.chdir d
  end

  def pwd
    puts Dir.pwd
  end

  def cat f
    open(f) { |io| print io.read }
  end

  def echo s
    @env.each { |name,value| s.gsub! /\$#{name}/, value.to_s }
    puts s
  end
  
  def let name, value
    @env[name] = value
  end

end

sh = BasicShell.new

if ARGV[0]
  
  open(ARGV[0]) do |io|
    
    io.each do |line|
      sh.instance_eval line
    end
    
  end
  
else

  puts "welcome"

  loop do
    print sh.env["prompt"]
    input = $stdin.gets
    break unless input

    begin
      sh.instance_eval input
    rescue => e
      puts "Bad Command #{e.message}"
    end

  end

  puts "goodbye"
  
end