excel_concat.rb

##  Concatenates a subset of columns in Excel amongst multiple sheets into one dump

require "rubygems"
require "active_support"
require "roo"
require "faster_csv"

COLUMNS = ["A", "B"]  # Column names of whatever you want

[].tap do |o|
  Excel.new("/full/path/to/file.csv").sheets.each do |sheet|
    2.upto(sheet.last_row) do |i|
      o << COLUMNS.map {|c| sheet.cell(i, c) }
    end
  end
end.to_csv

# Or this crazier way using triply-nested array mapping and depth-flattening...
Excel.new("/full/path/to/file.csv").sheets.map do |sheet|
  [2..sheet.last_row].map do |i|
    COLUMNS.map {|c| sheet.cell(i, c) }
  end
end.flatten(1).to_csv