command line tool for inline-editing (edit_inline PATTERN(regexp) REPACEMENT(ruby code outputting string) FILE(path to file))

edit_inline.rb

#!/usr/bin/env ruby
require 'open3'
require 'optparse'

script_name = File.basename($0)

options = {}
option_parser = OptionParser.new do |opts|
  opts.banner = <<-HEREDOC
    Usage:

        #{script_name} PATTERN REPLACEMENT FILE

    Example:

      #{script_name} 'name="(.*?)"' '"name: \#{$1.to_i}"' code.rb

  HEREDOC

  opts.on("-w", "--write", "Write to file") do
    options[:write] = true
  end

  opts.on("-d", "--diff", "Show diff") do
    options[:diff] = true
  end

  opts.on("-h", "--help", "Show help") do |o|
    puts option_parser
    exit
  end
end
option_parser.parse!

if ARGV.length == 3
  pattern, replacement, file = ARGV
else
  puts option_parser
  exit
end

matcher = Regexp.new(pattern, Regexp::MULTILINE)
body = File.read(file)
new_body = body.gsub(matcher){|| eval(replacement) }

if options[:diff]
  Open3.pipeline_w("diff #{file} -") {|i| i.puts new_body }
elsif options[:write]
  File.write(file, new_body)
else
  puts new_body
end