json - 处理 JSON 返回的空值

Question

我正在运行 ruby​​ 1.9。我有这段代码，它从这两个 /usr/sbin/storcli/c0/bbu show j 中提取 Status 和 State 的值 & /usr/sbin/storcli/c0/cv show j 命令。

#!/usr/bin/ruby
require 'json'

output_bbu = %x{/usr/sbin/storcli /c0/bbu show j}
output_cv = %x{/usr/sbin/storcli /c0/cv show j}

begin
        j = JSON.parse(output_bbu)
        k = JSON.parse(output_cv)
        result = j["Controllers"][0]["Command Status"]["Status"]

        ### I'm not sure how to get the value of "State" and store it in "status" variable.

        status = k["Controllers"][0]["Response Data"]["Cachevault_Info"][0]["State"]
        status = j["Controllers"][0]["Response Data"]["BBU_Info"][0]["State"]

        ###
rescue Exception => e
        puts "CRITICAL: error reading BBU status: #{e}"
        exit 2
end

if result != 'Success'
        puts "CRITICAL: command not successful, result: #{result}"
        exit 2
end

问题:

storcli/c0/cv show j 或 storcli/c0/bbu show j 两个命令之一在“状态”变量中返回空值，脚本失败并显示错误

undefined method `[]' for nil:NilClass

storcli/c0/cv show j 可以返回“State”的 nil 值，或者 storcli/c0/bbu show j 可以返回 nil。所以我想做的是将“State”的值存储在变量“status”中。

命令输出示例，

$ storcli /c0/cv show j

{
"Controllers":[
{
        "Command Status" : {
                "Controller" : 0,
                "Status" : "Success",
                "Description" : "None"
        },
        "Response Data" : {
                "Cachevault_Info" : [
                        {
                                "Model" : "CVPM02",
                                "State" : "Optimal",
                                "Temp" : "35C",
                                "Mode" : "-",
                                "MfgDate" : "2013/09/17"
                        }
                ]
        }
}
]
}

看，这里它返回了“State”的值作为“Optimal”，所以我想将它的值存储在变量“status”中。

零的示例输出，

$ storcli /c0/bbu show j

{
"Controllers":[
{
        "Command Status" : {
                "Controller" : 0,
                "Status" : "Failure",
                "Description" : "None",
                "Detailed Status" : [
                        {
                                "Ctrl" : 0,
                                "Status" : "Failed",
                                "Property" : "-",
                                "ErrMsg" : "use /cx/cv",
                                "ErrCd" : 1001
                        }
                ]
        }
}
]
}

Answer 1

由于您没有从一个命令中获得“响应数据”，您可以使用以下命令

status = k["Controllers"][0]
           .fetch(["Response Data"], {})
           .fetch(["Cachevault_Info"], {})
           .fetch([0], {})["Status"]
status ||= j["Controllers"][0]["Response Data"]["BBU_Info"][0]["State"]

对于 ||=，如果 status = k 的结果是 nil，它将设置 status = j