merge pdf files using ghostscript

pdfmerge.rb

#!/usr/bin/env ruby

if ARGV.first == "--help"
  puts <<-EOF
    usage: pdfmerge.rb SUMMARYFILE FILE1 FILE2 ...
    All Files have to be pdf-Files. Requires GhostScript (gs).
    Copyright 2009 Robert Riemann - licensed under GPL v2 or higher.
  EOF
  exit
end

begin
( ARGV.size - 1 ).times { |i|
  # raise RuntimeError, ARGV[i+1] + " doesn't exist. Aborting." unless File.exists? ARGV[i+1]
  raise ARGV[i+1] + " doesn't exist. Aborting." unless File.exists? ARGV[i+1]
}
rescue
  STDERR.puts $!
  exit 1
end

files = ARGV.join('" "')
%x[gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile="#{files}"]