Change track names in GPX files (ruby)

ChangeGpxTrackName.rb

#!/usr/bin/env ruby

# Script for assigning the date of a track in a GPX file as track name.
#
# Usage e.g $ ruby ChangeGpxTrackName.rb source.gpx target.gpx"
#
# Peter Vasil
# Date: 2011-01-31


require 'rexml/document'
include REXML

# unless ARGV.length == 1 || ARGV.length == 2 
#   puts "You should give a file name to work on!"
#   exit
# end
unless ARGV.length == 2 
  puts "You should give a source file path and destination file path!"
  exit
end

# if ARGV.length == 1
#   filename = ARGV[0]
#   new_filename = filename
# elsif ARGV.length == 2
#   filename = ARGV[0]
#   new_filename = ARGV[1]
# end
if ARGV.length == 2
  filename = ARGV[0]
  new_filename = ARGV[1]
end

gpxfile = File.new(filename)
doc = Document.new(gpxfile)
gpxfile.close

root = doc.root

puts "Processing GPX file..."
trk_num = 0
root.each_element('trk') do |elem|
  trk_num += 1
  old_name = elem.elements['name'].text
  new_name = elem.elements['trkseg/trkpt/time'].text
  puts "-----------------------------------------------"
  puts "Track " + trk_num.to_s
  puts "Old name: " + old_name
  puts "New name: " + new_name

  elem.elements[1].text = new_name
end
puts "-----------------------------------------------"

new_doc = Document.new
new_doc << XMLDecl.new
new_doc << root

new_gpxfile = File.open(new_filename, "w")
new_gpxfile.write new_doc
new_gpxfile.close

puts "Finished processing!"
puts "Wrote file '" + new_filename + "'"