shell編程學習之使用jq對json提取
jq命令允許直接在命令行下對JSON進行操作，包括分片、過濾、轉換等 ,jq是用C編寫，沒有運行時依賴，所以幾乎可以運行在任何系統上。預編譯的二進制文件可以直接在Linux、OS X和windows系統上運行，當然在linux和OS X系統你需要賦與其可執行權限；在linux系統中也可以直接用yum安裝。
下載地址 https://stedolan.github.io/jq/download/
本文主要介紹其使用，默認是已經安裝好的，沒有安裝的，請自行百度安裝。
現在先准備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 .
輸出如下：
[root@localhost ~]$ cat kumufengchun.json | jq .
{
"name": "kumufengchun",
"age": "18",
"city": "beijing",
"email": "kumufengchun@gmail.com",
"date": "Thursday",
"country": "China",
"company": [
"baidu",
"google",
"alibaba"
]
}
是已經格式化的json數據串，在linux系統下還高光顯示，key和value用不同的顏色表示，如下圖：
2.輸出某個字段或者某個索引的值
語法：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.輸出數組的值
語法：jq '.[
[root@localhost ~]$ jq '.company[1]' kumufengchun.json
"google"
[root@localhost ~]$ jq '.company[2]' kumufengchun.json
"alibaba"
4.輸出列表、數組的一部分，對其進行切片
語法：jq '.
[root@localhost ~]$ jq '.company[0:2]' kumufengchun.json
[
"baidu",
"google"
]
也可以省略開始的index，只有結束的index,如下，仍然是不包括結束index的值：
[root@localhost ~]$ jq '.company[:3]' kumufengchun.json
[
"baidu",
"google",
"alibaba"
]
也可以省略結束的index，只有開始的index,如下，輸出到最后：
[root@localhost ~]$ jq '.company[1:]' kumufengchun.json
[
"google",
"alibaba"
]
開始的索引也可以是負數，表示從后邊倒着數,從-1開始數：
[root@localhost ~]$ jq '.company[-2:]' kumufengchun.json
[
"google",
"alibaba"
]
5.循環輸出所有的值，如數組嵌套
語法：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.輸出多個索引的值，可以用逗號分割
語法： jq '.key1,.key2'
[root@localhost ~]$ jq '.name,.age' kumufengchun.json
"kumufengchun"
"18"
[root@localhost ~]$ jq '.date,.company[]' kumufengchun.json
"Thursday"
"baidu"
"google"
"alibaba"
如果是數組，用中括號括起來要輸出的鍵值，鍵值先寫誰，先輸出誰
[root@localhost ~]$ jq '.company[2,0]' kumufengchun.json
"alibaba"
"baidu"
7.用管道符號｜可以對其進行再次處理
語法：jq .[] | .
[root@localhost ~]$ jq '.[]|.name' test.json
"JSON"
"XML"
8.括號的作用
[root@localhost ~]$ echo 1 | jq '(.+2)*5'
15
[root@localhost ~]$ echo {1,2,3} | jq '(.+2)*5'
15
20
25
9.length求長度
如果是字符串是求的字符串的長度，如果是數組則求得是數組的長度
[root@localhost ~]$ cat kumufengchun.json | jq '.[] | length'
12
2
7
22
8
5
3
10.輸出所有的keys
語法： jq keys
[root@localhost ~]$ cat kumufengchun.json | jq 'keys'
[
"age",
"city",
"company",
"country",
"date",
"email",
"name"
]
輸出數組的keys:
[root@localhost ~]$ cat kumufengchun.json | jq '.company | keys'
[
0,
1,
2
]
11.判斷存不存在某個鍵
[root@localhost ~]$ cat kumufengchun.json | jq 'has("email")'
true
[root@localhost ~]$ cat kumufengchun.json | jq 'has("address")'
false