Recursively iterates over a directory containing Objective-C .h, .m and .pch files to check that their Apache license header is in the correct format (my first Ruby script...)

apache.rb

def copyright(fname, year, programmer)
  return "// #{fname}
//
// Copyright #{year} #{programmer}
//
// Licensed under the Apache License, Version 2.0 (the \"License\");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an \"AS IS\" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License."
end

def file_matches(path, years, programmers)
  file = File.open(path, "rb")
  contents = file.read
  basename = File.basename(path)
  file.close
  if not years.respond_to?("each")
    years = [years]
  end
  if not programmers.respond_to?("each")
    programmers = [programmers]
  end
  
  programmers.each do |programmer|
    years.each do |year|
      if contents.start_with?(copyright(basename, year, programmer))
        return true
      end
    end
  end
  return false
end

def walk(dir, years, programmers)
  if File.readable?(dir)
    Dir.foreach(dir) do |basename|
      next if basename == '.'or basename == '..'
      fullname = File.join(dir, basename)
      if File.directory?(fullname)
        walk(fullname, years, programmers)
      elsif basename.end_with?('.h', '.m', '.pch')
        if File.readable?(fullname)
          if not file_matches(fullname, years, programmers)
            puts basename
          end
        end
      end
    end
  end
end

if ARGV.length == 3
  directory = ARGV[0]
  programmers = ARGV[1].split(',')
  years = ARGV[2].split(',')
  walk(directory, years, programmers)
else 
  puts "Usage: ruby apache.rb directory programmers,by,comma years,by,comma"
end