inventory difference

exercise-differences.rb

#---
# 该程序是经典的文件操作程序。
# 在shell里运行：ruby exercise-difference.rb new-inventory.txt old-inventory.txt
#---

#检查运行本程序的参数是否设置正确
def check_usage   # (1)
  unless ARGV.length == 2 
    puts "Usage: differences.rb old-inventory new-inventory"
    exit
  end
end

#判断是否包含temp或recycler文件夹。
def boring?(line)
  line.split('/').include?('temp') or
    line.split('/').include?('recycler')
end

#用collect和reject方法来生成文件序列
def inventory_from(filename)
  inventory = File.open(filename)
  downcased = inventory.collect do | line |   
    line.chomp.downcase
  end
  downcased.reject do | line |
    boring?(line)
  end
end

#比较2个文件序列的差异
def compare_inventory_files(old_file, new_file) # (2)
  old_inventory = inventory_from(old_file)
  new_inventory = inventory_from(new_file)

  puts "The following files have been added:"
  puts new_inventory - old_inventory

  puts ""
  puts "The following files have been deleted:"
  puts old_inventory - new_inventory
end

#if I am the script running at the command line, check_usage and compare_inventory_files
if $0 == __FILE__ # (3)
  check_usage 
  compare_inventory_files(ARGV[0], ARGV[1]) 
end

inventory.rb

#---
#该程序打印出当前文件夹及其子文件夹的所有文件。
#你可以在textmate编辑器里按ctrl+R,看到程序运行的结果。
#在shell里运行$ruby inventory.rb > new-inventory.txt, 即在当前文件夹里生成txt文件。
#---

puts Dir.glob('**/*').each { | file | file.downcase }.sort

Enumerable是File对象的ancestors, 所以可以利用collect的方法。collect方法对文件里的每一行进行操作，结果返回一个array。

File.ancestors
=> [File, IO, File::Constants, Enumerable, Object, Kernel]

Variable $0 holds the name of the running script as it appeared on the command line. FILE is the name of the file it appears in.