combined.csv

merge_csv.rb

#!/usr/bin/env ruby

require 'rubygems'
require 'fastercsv'

input_files = [ ]

File.open('first.csv', 'w') do |f|
  f.write <<-CSV
first_name,last_name,employer
Fred,Flintstone,Bedrock Quarry
Clark,Kent,The Daily Planet
  CSV
end
input_files << 'first.csv'

File.open('second.csv', 'w') do |f|
  f.write <<-CSV
first_name,last_name,employer
Ralph,Kramden,Metro Bus
Joe,Friday,LAPD
  CSV
end
input_files << 'second.csv'

File.open('third.csv', 'w') do |f|
  f.write <<-CSV
first_name,last_name,employer
David,Hansson,37Signals
Jim,Weirich,EdgeCase
  CSV
end
input_files << 'third.csv'

output_file = 'combined.csv'

headers = nil
all_rows = []
input_files.each do |input_file|
 csv =  FasterCSV.table(input_file, :headers => true)
 in_headers, *in_rows = csv.to_a
 headers ||= in_headers
 all_rows.concat(in_rows)
end
FasterCSV.open(output_file, 'w') do |csv|
  csv << headers
  all_rows.each {|row| csv << row }
end