--- Net::FTP#retrlines(cmd, callback = nil)

    Сcmdǻꤵ줿ޥɤꡢƥȥǡ
    󤻤ޤԤĥƥȤɤ߹ߡcallbackǻꤵ줿
    Proc֥Ȥޤϥ֥åɤ߹ԤϤޤ 

    callback֥åά줿ɤ߹Ԥprintޤ

