require 'net/ftp'
ftp = Net::FTP.open('ftp.ibiblio.org') do |ftp|
  ftp.login
  ftp.chdir('pub/linux/')
  ftp.list('*Linux*') { |file| puts file }
  puts
  puts 'Saving a text file to disk while processing it.'
  ftp.gettextfile('How-do-I-get-Linux') { |line| puts "! #{line}" }
  puts "Saved #{File.size 'How-do-I-get-Linux'} bytes."
  puts
  puts 'Saving a binary file to disk.'
  ftp.getbinaryfile('INDEX.whole.gz')  
 puts "Saved #{File.size 'INDEX.whole.gz'} bytes."
end

-rw-r--r--   1 (?)      users    16979001 Jan  1 11:31 00-find.Linux.gz
-rw-rw-r--   1 (?) admin          73 Mar  9  2001 How-do-I-get-Linux
Saving a text file to disk while processing it.
!
!   Browse to http://metalab.unc.edu/linux/HOWTO/Installation-HOWTO.html
!
Saved 73 bytes.
Saving a binary file to disk.
Saved 213507 bytes.

-rw-r--r--   1 (?)      users      475798 Apr 12 10:01 00-find.Linux.gz
-rw-rw-r--   1 (?)      admin          73 Mar  9  2001 How-do-I-get-Linux

Saving a text file to disk while processing it.
! 
!   Browse to http://metalab.unc.edu/linux/HOWTO/Installation-HOWTO.html
! 
Saved 73 bytes.

Saving a binary file to disk.
Saved 213906 bytes.

ftp.login('leonardr', 'mypass')
class Net::FTP
  def processtextfile(remotefile)
    retrlines('RETR ' + remotefile) { |line| yield line }
  end
  def processbinaryfile(remotefile, blocksize=DEFAULT_BLOCKSIZE)
    retrbinary('RETR ' + remotefile, blocksize) { |data| yield data }
  end
end
require 'net/ftp'
Net::FTP.open('myisp.example.com') do |ftp|
  ftp.login('leonardr', 'mypass')
  ftp.chdir('public_html')
  ftp.puttextfile('index.html')
end

...

NoMethodError: undefined method `login' for nil:NilClass
	from (irb):15
SocketError: getaddrinfo: Name or service not known
	from /usr/lib/ruby/1.8/net/ftp.rb:159:in `initialize'
	from /usr/lib/ruby/1.8/net/ftp.rb:159:in `open_socket'
	from /usr/lib/ruby/1.8/net/ftp.rb:175:in `connect'
	from /usr/lib/ruby/1.8/monitor.rb:229:in `synchronize'
	from /usr/lib/ruby/1.8/net/ftp.rb:174:in `connect'
	from /usr/lib/ruby/1.8/net/ftp.rb:136:in `initialize'
	from /usr/lib/ruby/1.8/net/ftp.rb:113:in `open'
	from (irb):25