utf8_validator.rb

# requires Ruby 1.9
require "open-uri"

VALID_FORMAT = "[VALID] %s"
INVALID_FORMAT = "[INVALID] %s"

def valid?(url)
  open(url).read.force_encoding("UTF-8").valid_encoding?
end

def validate_with_output(url)
  format = if valid?(url)
    VALID_FORMAT
  else
    INVALID_FORMAT
  end

  puts format % url
end

ARGV.each {|arg| validate_with_output(arg) }