如何让grep从众多中挑出一个？

Question

我有以下grep声明：

kernelHash=$(grep -m 1 -o '"hashvalue": [^, }]*' $SecureBootJson | sed 's/^.*: //')

每晚都会生成一个新文件（请参阅下面的示例），并设置所有新的哈希值。有一个独特的文字，其中“hashvalue”（“asomething2”）使生活更轻松。 Grep只需要寻找“asomething2”。但是现在我需要在something2块中分配给“hashvalue”的hashvalue。我不得不将“asomething2”改为“hashvalue”。问题是该文件有15个“hashvalue”文字，我只需要它来查看第二个文件。我怎么能告诉grep只从文件中挑出第二个“hashvalue”？

以下是该文件的示例：

{
   "files":[
      {
         "something1":{
            "sources":{
               "asomething1":"3842d9bd57cd5b0b6f4388b55230a188e093b435d89093e5f90099d174167d71",
               "bsomething1":"229448f5d12e0e5c683136aef83243f8eec142873b9ebc48f3852a867aafee9d"
            },
            "hashvalue":"3536b8ad291ad33b0b39b59e59bec1c98a01473cfc0507a0e926b79fac580b6c",
            "type":"bootloader",
            "mode":"2ND"
         }
      },
      {
         "something2":{
            "sources":{
               "asomething2":"6685c4a147ca318f2e870b8a616fd2ccb188868ab10cceb7c68d5a4bda33c16f"
            },
            "hashvalue":"cda2e741d6229f670963f52ea5b6427e1fcdb9bc66bdfe338efcb70ac5b3d61c",
            "type":"image"
         }
      },
      {
         "something3":{
            "sources":{
               "asomething3":"4d9530a3047ef20d67b2d91380416925e9e8867f28db27e2a138e4c48d34b95b"
            },
            "hashvalue":"7f43440bb71de0c99b1f110f1fb73df36a63904d3e80d8c39b7fe34c99143fbe",
            "type":"image"
         }
      },
      {
         "something4":{
            "hashvalue":"613635f9749db37a133d81a7d70bcd8d2abc336576b30463561e9fc7ef02f31b",
            "type":"passthru"
         }
      },
      {
         "something5":{
            "hashvalue":"8cee68c3b2a4975b03f8fa2cab2bda7bd04646d43470503c0efdac7719ecc756",
            "type":"passthru"
         }
      },
      {
         "something6":{
            "hashvalue":"6a1b81d9a623df9a42e382008e531f67aff5cd64b292a403f01339e80edb14d6",
            "type":"passthru"
         }
      },
      {
         "something7":{
            "hashvalue":"200e162f014d6555820c5e69b80cba53ee19c4f289f2352833a0faf86b230031",
            "type":"passthru"
         }
      },
      {
         "something8":{
            "hashvalue":"4d9530a3047ef20d67b2d91380416925e9e8867f28db27e2a138e4c48d34b95b",
            "type":"passthru"
         }
      },
      {
         "something9":{
            "hashvalue":"07258ddb82082c71b81a760cd1c540ca35a52250cb8f94ca90b97514f0df7fff",
            "type":"manifest"
         }
      },
      {
         "something10":{
            "hashvalue":"74732b0224bdb1235670f0041d4cabb8010a3e2fcb55dea5ce003673b23f1e9a",
            "type":"manifest"
         }
      },
      {
         "something11":{
            "hashvalue":"d80dc4ada8e9b611803fbd4d28d37a621618c2c1b39b4d470a4e622b0dbf3f1d",
            "type":"manifest"
         }
      },
      {
         "something12":{
            "hashvalue":"84ff4132f25a7f6d468374afb9f1f4ba4711e67a3e5cce712d77368eecd45194",
            "type":"manifest"
         }
      },
      {
         "something13":{
            "hashvalue":"fdceda07f28179da26621ef9a72c2de0627af12afe7e6784590ec67d55a21820",
            "type":"manifest"
         }
      },
      {
         "something14":{
            "hashvalue":"5d77074465c752b9197bbf4b54e599173b9e49540a56784758862e502dea2519",
            "type":"manifest"
         }
      },
      {
         "something15":{
            "hashvalue":"a53a1a9129ca98b6d10f67a0a3e630ed4a1851ffedf96d91b79b41f61ea00d4b",
            "type":"manifest"
         }
      }
}

我想要的输出是分配给kernelHash的something2块中“hashvalue”的哈希值：

kernelHash = cda2e741d6229f670963f52ea5b6427e1fcdb9bc66bdfe338efcb70ac5b3d61c

Answer 1

grep 解决方案：

示例json文件input.json：

{
  "key1": "abc",
  "hashvalue":"cd11111111111111111sdfsdfw1111111",
  "key2": "def",
  "secure.data": {
       "hashvalue":"cda2e741d6229f670963f52ea5b6427e1fcdb9bc66bdfe3‌​38efcb70ac5b3d61c",
       "key3": "ghi"
  },
  "key4":"jkl",
  "hashvalue":"22222sfsdfsdfsdf33333333" 
}

提取第二个hashvalue并分配到变量kernelHash：

kernelHash=$(grep -Pzo '("hashvalue":)"[^"]+",[\s\S]+?\1\K"[^"]+"' input.json)
echo "$kernelHash" 
"cda2e741d6229f670963f52ea5b6427e1fcdb9bc66bdfe3‌​38efcb70ac5b3d61c"