shell编程学习之使用jq对json提取
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，请自行百度安装。
目录
现在先准备json串，如下kumufengchun.json：
{"name":"kumufengchun","age":"18","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": "18",
"city": "beijing",
"email": "kumufengchun@gmail.com",
"date": "Thursday",
"country": "China",
"company": [
"baidu",
"google",
"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 '.
[root@localhost ~]$ jq .name kumufengchun.json
"kumufengchun"
[root@localhost ~]$ jq '.name' kumufengchun.json
"kumufengchun"
[root@localhost ~]$ jq '.company' kumufengchun.json
[
"baidu",
"google",
"alibaba"
]
3.输出数组的值
语法：jq '.[
[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 '.
[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",
"google",
"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"
"18"
"beijing"
"kumufengchun@gmail.com"
"Thursday"
"China"
[
"baidu",
"google",
"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"
"18"
[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 .[] | .
[root@localhost ~]$ jq '.[]|.name' test.json
"JSON"
"XML"
8.括号的作用
[root@localhost ~]$ echo 1 | jq '(.+2)*5'
15
[root@localhost ~]$ echo {1,2,3} | jq '(.+2)*5'
15
20
25
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'
12
2
7
22
8
5
3
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'
[
0,
1,
2
]
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