rename pdf files i downloader around the internet

rename.rb

#!/usr/bin/env ruby
# -*- coding: utf-8 -*-

# easy to break use at your own risk

# this script renames pdf files in a folder (and subfoler) (on unixy machines)
# with a naive heuristic to find the title (that unfortunately is never in the *title* metadata)

require 'pdf-reader'

def is_title? str
  str =~ /^[\w\s:,\(\)-\.\|\?#]+$/
end

def find_title file
  ln = "\n".codepoints.first
  # look for "\n\n" pattern
  reader = PDF::Reader.new file
  last_codepoint = nil
  header = reader.page(1).text.each_codepoint.slice_before do |cp|
    lc = last_codepoint
    last_codepoint = cp
    [cp, lc] == [ln, ln]
  end.first.pack("U*").squeeze(" ").tr("/’\"", "_''")
  # remove "\n" until it matches our criteria
  title = header.split("\n").slice_before { |line| !is_title?(line) }.first.map(&:strip).join(" | ")
  if is_title? title
    return title
  else
    STDERR.puts "couldnt find a valid title for file '#{File.basename file}' -- best match is '#{title}' /// #{file}"
  end
end

`find "/Users/freakhill/Dropbox/learn/" -name "*.pdf"`.split("\n").each do |file|
  begin
    (title = find_title file) or next
    newfile = File.join(File.dirname(file),"#{title}.pdf")
    next if File.exists?(newfile)
    `mv "#{file}" "#{newfile}"`
    puts "#{File.basename file} => '#{title}' PROCESSED!"
  rescue Exception => e
    puts "failed on #{file} => #{e}"
  end
end