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如何在命令行中 grep JSON 键的值？

tag-icon • tag-icon command-line text-processing aws
如何在命令行中 grep JSON 键的值？

这是此命令的 JSON 输出aws logs list-log-groups，我需要从中获取第一个“arn”值。我该怎么做？

{
    "logGroups": [
        {
            "logGroupName": "alla",
            "creationTime": 1594638588652,
            "metricFilterCount": 0,
            "arn": "arn:aws:logs:us-east-1:12345678910:log-group:*:*",
            "storedBytes": 0
        },
        {
            "logGroupName": "mahi",
            "creationTime": 1594638580461,
            "metricFilterCount": 0,
            "arn": "arn:aws:logs:us-east-1:12345678910:log-group:*:*",
            "storedBytes": 0
        }
    ]
}

答案1

我最近发现了一个工具叫gron。

gron <<'END_JSON'
{
    "logGroups": [
        {
            "logGroupName": "alla",
            "creationTime": 1594638588652,
            "metricFilterCount": 0,
            "arn": "arn:aws:logs:us-east-1:12345678910:log-group:*:*",
            "storedBytes": 0
        },
        {
            "logGroupName": "mahi",
            "creationTime": 1594638580461,
            "metricFilterCount": 0,
            "arn": "arn:aws:logs:us-east-1:12345678910:log-group:*:*",
            "storedBytes": 0
        }
    ]
}
END_JSON

json = {};
json.logGroups = [];
json.logGroups[0] = {};
json.logGroups[0].arn = "arn:aws:logs:us-east-1:12345678910:log-group:*:*";
json.logGroups[0].creationTime = 1594638588652;
json.logGroups[0].logGroupName = "alla";
json.logGroups[0].metricFilterCount = 0;
json.logGroups[0].storedBytes = 0;
json.logGroups[1] = {};
json.logGroups[1].arn = "arn:aws:logs:us-east-1:12345678910:log-group:*:*";
json.logGroups[1].creationTime = 1594638580461;
json.logGroups[1].logGroupName = "mahi";
json.logGroups[1].metricFilterCount = 0;
json.logGroups[1].storedBytes = 0;

此工具将 JSON 符号逐行转换为易于检索的 javascript。

$ arn=$(gron <<'END_JSON' | sed -En '/json\.logGroups\[0\]\.arn/ s/^[^"]*"(.*)";$/\1/p'
{
  ...
}
END_JSON
)
$ echo "$arn"
arn:aws:logs:us-east-1:12345678910:log-group:*:*

答案2

使用jq：

aws logs list-log-groups | jq -r '.logGroups[0].arn'

输出：

arn:aws:logs:us-east-1:929815623526:log-group:alla:

jq可以从universe存储库：

sudo apt install jq

jq是解析的首选json，但如果jq出于某种原因没有选择，并且您知道格式不会改变，您可以使用grep -P和head -n1：

aws logs list-log-groups | grep -Po '"arn": "\K[^"]*' | head -n1

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