linux shell json操作命令 jq 简介

jq命令允许直接在命令行下对JSON进行操作，包括分片、过滤、转换等,jq是用C编写，没有运行时依赖，所以几乎可以运行在任何系统上。预编译的二进制文件可以直接在Linux、OS X和windows系统上运行，当然在linux和OS X系统你需要赋与其可执行权限；在linux系统中也可以直接用yum安装。

下载地址 https://stedolan.github.io/jq/download/

本文主要介绍其使用，默认是已经安装好的，没有安装的，请自行安装。

现在先准备json串，如下kumufengchun.json：

{"name":"kumufengchun","age":"","city":"beijing","email":"kumufengchun@gmail.com","date":"Thursday","country":"China","company":["baidu","google","alibaba"]}"

如下test.json:

[{"name":"JSON","good":true},{"name":"XML","good":false}]

1.用jq .直接查看

jq . kumufengchun.json

或者

cat kumufengchun.json | jq .

输出如下：

[root@localhost ~]$ cat kumufengchun.json | jq .
{
"name": "kumufengchun","age": "","city": "beijing","email": "kumufengchun@gmail.com","date": "Thursday","country": "China","company": [
"baidu","alibaba"
]
}

是已经格式化的json数据串，在linux系统下还高光显示，key和value用不同的颜色表示，如下图：

2.输出某个字段或者某个索引的值

语法：jq '.<key>' ,这里key是字段名称

[root@localhost ~]$ jq .name kumufengchun.json
"kumufengchun"

[root@localhost ~]$ jq '.name' kumufengchun.json
"kumufengchun"

[root@localhost ~]$ jq '.company' kumufengchun.json
[
"baidu","alibaba"
]

3.输出数组的值

语法：jq '.[<value>]',这里value是数组的索引整数值

[root@localhost ~]$ jq '.company[1]' kumufengchun.json
"google"

[root@localhost ~]$ jq '.company[2]' kumufengchun.json
"alibaba"

4.输出列表、数组的一部分，对其进行切片

语法：jq '.<list-key>[s:e]',返回的是数组或者列表的index从s开始（包括s）到e结束（不包括e）

[root@localhost ~]$ jq '.company[0:2]' kumufengchun.json
[
"baidu","google"
]

也可以省略开始的index，只有结束的index,如下，仍然是不包括结束index的值：

[root@localhost ~]$ jq '.company[:3]' kumufengchun.json
[
"baidu","alibaba"
]

也可以省略结束的index，只有开始的index,如下，输出到最后：

[root@localhost ~]$ jq '.company[1:]' kumufengchun.json
[
"google","alibaba"
]

开始的索引也可以是负数，表示从后边倒着数,从-1开始数：

[root@localhost ~]$ jq '.company[-2:]' kumufengchun.json
[
"google","alibaba"
]

5.循环输出所有的值，如数组嵌套

语法：jq '.[]'

[root@localhost ~]$ jq '.[]' test.json
{
"name": "JSON","good": true
}
{
"name": "XML","good": false
}

[root@localhost ~]$ jq '.[]' kumufengchun.json
"kumufengchun"
""
"beijing"
"kumufengchun@gmail.com"
"Thursday"
"China"
[
"baidu","alibaba"
]

6.输出多个索引的值，可以用逗号分割

语法： jq '.key1,.key2'

[root@localhost ~]$ jq '.name,.age' kumufengchun.json
"kumufengchun"
""

[root@localhost ~]$ jq '.date,.company[]' kumufengchun.json
"Thursday"
"baidu"
"google"
"alibaba"

如果是数组，用中括号括起来要输出的键值，键值先写谁，先输出谁

[root@localhost ~]$ jq '.company[2,0]' kumufengchun.json
"alibaba"
"baidu"

7.用管道符号｜可以对其进行再次处理

语法：jq .[] | .<key1>

[root@localhost ~]$ jq '.[]|.name' test.json
"JSON"
"XML"

8.括号的作用

[root@localhost ~]$ echo | jq '(.+2)*5'

[root@localhost ~]$ echo {,} | jq '(.+2)*5'

9.length求长度，如果是字符串是求的字符串的长度，如果是数组则求得是数组的长度

[root@localhost ~]$ cat kumufengchun.json | jq '.[] | length'

10.输出所有的keys

语法： jq keys

[root@localhost ~]$ cat kumufengchun.json | jq 'keys'
[
"age","city","company","country","date","email","name"
]

输出数组的keys:

[root@localhost ~]$ cat kumufengchun.json | jq '.company | keys'
[,]

11.判断存不存在某个键

[root@localhost ~]$ cat kumufengchun.json | jq 'has("email")'
true
[root@localhost ~]$ cat kumufengchun.json | jq 'has("address")'
false

12.向josn文件中追加数据

实例1：以 /etc/docker/daemon.json 为例

原本数据如下：

{
  "dns": [
    "114.114.114.114","8.8.8.8"
  ],"registry-mirrors": [
    "http://hub-mirror.c.163.com","https://docker.mirrors.ustc.edu.cn","https://registry.docker-cn.com"
  ]
}

执行追加命令

cat /etc/docker/daemon.json | jq '.["log-driver"]="json-file"' > tmp.json && mv -f tmp.json /etc/docker/daemon.json
cat /etc/docker/daemon.json | jq '.["log-opts"]={"max-size":"500m","max-file":"3"}' > tmp.json && mv -f tmp.json /etc/docker/daemon.json

最终数据如下：

{
  "dns": [
    "114.114.114.114","https://registry.docker-cn.com"
  ],"log-driver": "json-file","log-opts": {
    "max-size": "500m","max-file": "3"
  }
}

实例2：

objName="objName"
objJSON='{"test": "json"}'
echo '{"data":{}}' |
  jq --arg     objectName "$objName" \
     --argjson jsonString "$objJSON" \
    '.data[$objectName] += $jsonString'

输出：

{
  "data": {
    "objName": {
      "test": "json"
    }
  }
}