ファイル内の文字列を一括置換する．

replace.rb

#! /usr/bin/ruby -w
# encoding: utf-8

require 'optparse'
require 'fileutils'

bak = from = to = nil
#引数解析
opt = OptionParser.new
opt.on("-b", "--backup <extention>", String) {|val| bak = val}
opt.on("-f", "--from   <from>"     , Regexp) {|val| from = val}
opt.on("-t", "--to     <to>"       , String) {|val| to   = val}
begin
  opt.parse!(ARGV)
rescue
  print opt.to_s
  exit
end

raise opt.to_s if bak.nil? or from.nil? or to.nil?

ARGV.each do |filename|
  backup = filename + bak
  lines = open(filename, "r+").readlines
  replaced_lines = lines.map {|line| line.gsub(from,to) }
  next if replaced_lines.eql? lines
  begin
    FileUtils.cp(filename, backup)
    f = open(filename, "w")
    replaced_lines.each {|line| f.write(line)}
  rescue
    FileUtils.rm(filename)
    FileUtils.mv(backup, filename)
  end
end