/usr/bin/nokogiri is in ruby-nokogiri 1.6.3.1+ds-1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76  | #!/usr/bin/ruby
require 'optparse'
require 'open-uri'
require 'irb'
require 'uri'
require 'nokogiri'
parse_class = Nokogiri
encoding = nil
opts = OptionParser.new do |opts|
  opts.banner = "Nokogiri: an HTML, XML, SAX, and Reader parser"
  opts.define_head "Usage: nokogiri <uri|path> [options]"
  opts.separator ""
  opts.separator "Examples:"
  opts.separator "  nokogiri http://www.ruby-lang.org/"
  opts.separator "  nokogiri ./public/index.html"
  opts.separator "  curl -s http://nokogiri.org | nokogiri -e'p $_.css(\"h1\").length'"
  opts.separator ""
  opts.separator "Options:"
  opts.on("--type [TYPE]", [:xml, :html]) do |v|
    parse_class = {:xml => Nokogiri::XML, :html => Nokogiri::HTML}[v]
  end
  opts.on("-E", "--encoding encoding", "Read as encoding (default #{encoding})") do |v|
    encoding = v
  end
  opts.on("-e command", "Specifies script from command-line.") do |v|
    @script = v
  end
  opts.on("--rng <uri|path>", "Validate using this rng file.") do |v|
    @rng = open(v) {|f| Nokogiri::XML::RelaxNG(f)}
  end
  opts.on_tail("-?", "--help", "Show this message") do
    puts opts
    exit
  end
  opts.on_tail("-v", "--version", "Show version") do
    puts Nokogiri::VersionInfo.instance.to_markdown
    exit
  end
end
opts.parse!
uri = ARGV.shift
if uri.to_s.strip.empty? && $stdin.tty?
  puts opts
  exit 1
end
if $stdin.tty?
  @doc = parse_class.parse(open(uri).read, nil, encoding)
else
  @doc = parse_class.parse($stdin, nil, encoding)
end
$_ = @doc
if @rng
  @rng.validate(@doc).each do |error|
    puts error.message
  end
else
  if @script
    eval @script, binding, '<main>'
  else
    puts "Your document is stored in @doc..."
    IRB.start
  end
end
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