比较文本行

lines-cmp

#!/bin/env ruby

argv = ARGV
self_name = File.basename($0)

DIFFERENCE = :d
INTERSECTION = :i
UNION = :u

if argv.length != 3
  puts "Usage: #{self_name} <mode> <file1> <file2>"
  puts "Mode:"
  puts "  d: difference, elements in file1 but not in file2"
  puts "  i: intersection, elements in file1 and file2"
  puts "  u: union, elements in file1 or file2, duplicates removed"
  exit 1
end

mode, file1, file2 = argv

mode = case mode
       when 'd'
         DIFFERENCE
       when 'i'
         INTERSECTION
       when 'u'
         UNION
       else
         puts "Unknown mode: #{mode}"
         exit 1
       end

file1 = File.new file1
file2 = File.new file2

file1_lines = file1.readlines
file2_lines = file2.readlines

case mode
when DIFFERENCE
  puts file1_lines - file2_lines
when INTERSECTION
  puts file1_lines & file2_lines
when UNION
  puts file1_lines | file2_lines
else
  # unreachable
  abort
end