interactive.rb

# replace HERE interactive, execute command.
# for example: ruby interactive.rb expr HERE + HERE + HERE

require 'readline'
require 'shellwords'

HERE = /HERE/

def read_input
  Readline.readline("> ", true)
end

command_template = ARGV

loop {
  command = command_template.clone
  command.map!{|fragment|
    fragment.gsub(HERE) {
      puts "command: #{command.join(' ')}"
      read_input
    }
  }
  puts "execute #{command.join(' ')}? (y/N)"
  next unless read_input == 'y'
  system *command
}