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Question

我想设置一个布尔变量来切换Net::Telnet模块在日志路径，即：

telnetdebug = false 
telnetlog = false 
telnetlogfile = '/var/log/mcacheMonitor.telnet.log' 

xmr = Net::Telnet.new("Host" => host, 
         "Timeout" => 10, 
         "Prompt" => /[#]\z/n, 
         'Waittime' => 0, 
         'Dump_log' => telnetdebug ? "mcmsDebug.log" : nil, 
         'Output_log' => telnetlog ? telnetlogfile : nil) 

但是这个代码产生以下错误：

C:/Ruby192/lib/ruby/1.9.1/net/telnet.rb:300:in `initialize': can't convert nil into String (TypeError) 
     from C:/Ruby192/lib/ruby/1.9.1/net/telnet.rb:300:in `open' 
     from C:/Ruby192/lib/ruby/1.9.1/net/telnet.rb:300:in `initialize' 
     from mcw.rb:26:in `new' 
     from mcw.rb:26:in `<main>' 

Answer 1

telnet文档是cheating。它表示默认值为零，但实际上不是。如果它有一个键'Dump_log'，则检查参数的散列。如果是，则该值用作文件名。所以这应该工作：

telnet_arguments={"Host" => host, 
        "Timeout" => 10, 
        "Prompt" => /[#]\z/n, 
        'Waittime' => 0} 
telnet_arguments['Dump_log'] = "mcmsDebug.log" if telnetdebug 
telnet_arguments['Output_log'] = telnetlogfile if telnetlog 

xmr = Net::Telnet.new(telnet_arguments)