net_ssh_remove.rb

# In here, we monkey-patch Net::SSH. Beware, there be dragons.
# Net::SSH can add hosts to the known_hosts file, but can't remove
module Net; module SSH
  class KnownHosts
    
    # Looks in all user known host files (see KnownHosts.hostfiles) and tries to
    # remove an entry for the given host and key to the first file it is able to.
    def self.remove(host, options={})
      hostfiles(options, :user).each do |file|
        begin
          KnownHosts.new(file).remove(host)
          return
        rescue SystemCallError
          # try the next hostfile
        end
      end
    end
    
    # Tries to delete an entry from the current source file for the given host
    # If it is unable to (because the file is not writable, for instance),
    # an exception will be raised.
    def remove(host)
      keys = File.readlines(source)
      keys.delete_if{|host_info| host_info.split[0] == host}
      
      File.open(source, "w") do |f| 
        keys.each{|line| f.puts(line)}
      end
    end
  end
end; end