How can I create a program to create multiple files from one template with different values inside?

Question

I need to create 1500+ ruby files from a template for some testing I'm doing with Selenium.

The template looks like this:

class $CLASS_NAME

require "spec"

attr_accessor :title

include Spec::Example::ExampleGroupMethods
include Spec::Matchers


def initialize  
  @title = "$OLD_URL -> $NEW_URL"
end


def execute(selenium)
  selenium.open "$OLD_URL"
  sleep 1
  puts 'Opening...'
  sleep 1
  url = selenium.get_location
  puts 'Grabbing location...'
  sleep 1
  puts 'The URL is ' + url 
  puts 'Doing match...'
  sleep 1
  /$NEW_URL/.match(url).should_not be nil

  puts "\n##### Success! #####\n\r"

end # execute

I have a load of URL's I need to insert - one into each file, replacing '$OLD_URL' and '$NEW_URL'.

Is there anyway to do something like this?

x = 0
while (x < 1500)
{
open template.rb
find all instances of $CLASS_NAME and replace with xxx from classnames.txt
find all instances of $OLD_URL and replace with xxx from listofurls.csv
find all instances of $NEW_URL and replace with xxx from listofurls.csv
save file as ('redirect_' + 'x++')
x++
}

Answer 1

Read the contents of template.rb to a string, then use String#gsub to edit the template inside the loop and save the modified template.

Answer 2

The proper way to do it is using the ERB library.

The code below will generate two files according to predefined template.

require "erb"

File.open("template.erb") do |io|
  template = ERB.new io.read

  files = {:anecdote => "There are 10 types of people in the world.",
           :story => "Once upon a time..."}

  files.each do |file, contents|
    File.open "#{file}.txt", "w" do |out| 
      out.puts template.result binding
    end
  end
end

When template.erb looks like:

Title <%= file %>
<%= "=" * 40 %>
<%= contents %>
<%= "=" * 40 %>

Here is the contents of aneqdote.txt:

Title anecdote
========================================
There are 10 types of people in the world.
========================================