# jq用法

jq用法

Linux下处理json字符串利器，用过的人都说好！

1 测试用json文件

^_^ kevin@TM1701-b38cbc23:~$ cat  service_health_return.json 
{"status":"UP","components":{"db":{"status":"UP","details":{"database":"PostgreSQL","validationQuery":"isValid()"}},"discoveryComposite":{"status":"UP","components":{"discoveryClient":{"status":"UP","details":{"services":["gc-system-service","gc-policy-service","gc-gateway","gc-apply-service","gc-attachment-service","gc-party-service","gc-thirdparty-service","gc-travel-service","gc-message-service","gc-app-service","gc-endorse-service","gc-platform-service","gc-renewal-service","gc-product-service","gc-client-service","gc-workflow-service","gc-certify-service","gc-report-service","gc-auth-service","gc-payment-service","gc-agent-service","gc-claim-service","gc-finance-service","gc-batch-service"]}}}},"diskSpace":{"status":"UP","details":{"total":48420556800,"free":26521001984,"threshold":10485760,"exists":true}},"nacosConfig":{"status":"UP"},"nacosDiscovery":{"status":"UP"},"ping":{"status":"UP"},"refreshScope":{"status":"UP"},"sentinel":{"status":"UNKNOWN","details":{"dataSource":{"degrade-sentinel-nacos-datasource":{"status":"UP"},"authority-sentinel-nacos-datasource":{"status":"UP"},"flow-sentinel-nacos-datasource":{"status":"UP"},"param-flow-sentinel-nacos-datasource":{"status":"UP"},"system-sentinel-nacos-datasource":{"status":"UP"}},"enabled":true,"dashboard":{"description":"the dashboard servers [[Tuple2{r1=192.168.11.74, r2=13060}]] one of them can't be connected","status":"UNKNOWN"}}}}}

注意：

json 数组的键命名必须为下划线"_"，不能为"-"，否则解析不了

2 用法

2.1 根据key获取value：

• 说明

# 格式化json
cat  service_health_return.json  | jq  .

# 第一级key值的获取（替换'{某key}'为具体key）
cat  service_health_return.json  | jq  .{某key}

# 第N级key值的获取（替换'{某key*}'为具体key）
cat  service_health_return.json  | jq  .{某key1}.{某key2}.{某keyN}

# 输出数组中的值
cat  service_health_return.json  | jq  .{某key1}.{某key2}.{某keyN}[]

注意：

在使用中发现：jq后面的参数加不加【‘’】都行

解析不存在的元素，会返回null

• 示例：

# 格式化输入（service_health_return.json太长）
^_^ kevin@TM1701-b38cbc23:~$ echo '{"foo": 0}' | jq .
{
  "foo": 0
}

# 获取key的值
^_^ kevin@TM1701-b38cbc23:~$ cat service_health_return.json |jq .db
"UP"
^_^ kevin@TM1701-b38cbc23:~$ cat service_health_return.json |jq .components.db
{
  "status": "UP",
  "details": {
    "database": "PostgreSQL",
    "validationQuery": "isValid()"
  }
}
^_^ kevin@TM1701-b38cbc23:~$ cat service_health_return.json |jq .components.discoveryComposite.components.discoveryClient.details.services
[
  "gc-system-service",
    "gc-gateway",
  "gc-finance-service",
  "gc-batch-service"
]
^_^ kevin@TM1701-b38cbc23:~$ cat service_health_return.json |jq .components.discoveryComposite.components.discoveryClient.details.services[]
"gc-system-service"
"gc-gateway"
"gc-finance-service"
"gc-batch-service"

2.2 内建函数：keys，has

• 说明

- keys  是用来获取JSON中的key元素的，查找json中所有的键
- has   是用来是判断是否存在某个key

• 示例

# 获取key
^_^ kevin@TM1701-b38cbc23:~$ cat service_health_return.json | jq 'keys'
[
  "components",
  "status"
]
^_^ kevin@TM1701-b38cbc23:~$ cat service_health_return.json | jq 'keys' | jq .[]
"components"
"status"


# 获取下一级key
^_^ kevin@TM1701-b38cbc23:~$ cat service_health_return.json | jq .components | jq 'keys'
[
  "db",
  "discoveryComposite",
  "diskSpace",
  "nacosConfig",
  "nacosDiscovery",
  "ping",
  "refreshScope",
  "sentinel"
]


# 查询是否存在key
^_^ kevin@TM1701-b38cbc23:~$ cat service_health_return.json | jq 'has("components")'
true
^_^ kevin@TM1701-b38cbc23:~$ cat   service_health_return.json  | jq 'has("db")'
false

3 Help输出

^_^ kevin@TM1701-b38cbc23:~$ jq --help
jq - commandline JSON processor [version 1.6]

Usage:	jq [options]  [file...]
	jq [options] --args  [strings...]
	jq [options] --jsonargs  [JSON_TEXTS...]

其中一些选项包括：

-c  紧凑，而不是漂亮的打印输出；
-n  使用“null”作为单个输入值；
-e  根据输出设置退出状态代码；
-s  将所有输入读取（slurp）到一个数组中；对其应用过滤器；
-r  输出原始字符串，而不是JSON文本；
-R  读取原始字符串，而不是JSON文本；
-C  为JSON着色；
-M  单色（不要将JSON着色）；
-S  对输出对象的键进行排序；
--tab          使用制表符进行缩进；

--arg a v      将变量$a设置为值＜v＞；
--argjson a v  将变量$a设置为JSON值＜v＞；

--slurpfile a f   将变量$a设置为从读取的JSON文本数组；
--rawfile   a f   将变量$a设置为由的内容组成的字符串；

--args        剩余的参数是字符串参数，而不是文件；
--jsonargs    剩余的参数是JSON参数，而不是文件；

--    终止自变量处理；

命名参数也可用作$ARGS.Named[]，而位置参数可用作$ARGS.positional[]。

4 最后

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