spreadsheet-modify.rb

#!/usr/bin/env ruby
require 'spreadsheet'

input_path = ARGV[0] or abort('Expecting .xls file as argument')
output_path = input_path.sub(/\.xls$/, '-out.xls')

book = Spreadsheet.open(input_path)

# This is a fix/workaround - modifying each sheet in the workbook.
# Without it, the output file doesn't open at all
#
# After resaving the file in Excel for Mac 2011 the output file
# generates warning on open and is sometimes missing data
#
book.worksheets.each do |sheet|
  sheet.each(0) { |row| row.replace row }
end

# Without the code above this line breaks the output file completley
book.worksheet(0).row(0)[0] = ''

book.write(output_path)