1. 简介

json是一种轻量级的数据交换格式，应用范围非常广泛。在Linux系统下使用jq工具可以非常方便的处理json，官方给的定义是：

A jq program is a “filter”: it takes an input, and produces an output. There are a lot of builtin filters for extracting a particular field of an object, or converting a number to a string, or various other standard tasks.

通俗的说就是一个能够接受json，处理json，输出json的程序，反正很好用。

安装起来也非常的方便，直接使用yum即可安装。

[root@test-dhcp ~]# yum install jq

2. 基本操作

1. 创建

[root@test-dhcp ~]# jq -n {a:1}
{
  "a": 1
}
[root@test-dhcp ~]# jq -n '{a:"test"}'
{
  "a": "test"
}

1. 合并

[root@test-dhcp ~]# jq -n '{a:"test"} + {b:2}'
{
  "a": "test",
  "b": 2
}
[root@test-dhcp ~]# jq -n '{a:"test"} + {b:2} + {c:"testc"}'
{
  "a": "test",
  "b": 2,
  "c": "testc"
}

1. 删除

[root@test-dhcp ~]# cat test.json 
{"a": "test","b": 2, "c": "testc"}
[root@test-dhcp ~]# cat test.json |jq .
{
  "a": "test",
  "b": 2,
  "c": "testc"
}
[root@test-dhcp ~]# cat test.json |jq 'del(.b)'
{
  "a": "test",
  "c": "testc"
}

1. 更新

[root@test-dhcp ~]# cat test.json 
{"a": "test","b": 2, "c": "testc"}
[root@test-dhcp ~]# cat test.json |jq '.b="testb"'
{
  "a": "test",
  "b": "testb",
  "c": "testc"
}
[root@test-dhcp ~]# cat test.json |jq '. + {d:4}'
{
  "a": "test",
  "b": 2,
  "c": "testc",
  "d": 4
}
[root@test-dhcp ~]# cat test.json |jq '. + {d:4}' |jq '.d={dd:5}'
{
  "a": "test",
  "b": 2,
  "c": "testc",
  "d": {
    "dd": 5
  }
}

1. 查询

[root@test-dhcp ~]# cat test.json |jq .
{
  "a": "test",
  "b": 2,
  "c": "testc",
  "d": {
    "dd": 5
  }
}
[root@test-dhcp ~]# cat test.json |jq '. + {d:4}' |jq '.d={dd:5}' |jq .d.dd
5
[root@test-dhcp ~]# echo '{"a":1,"b":2}' |jq '[.a,.b]'
[
  1,
  2
]

1. 查看数据类型

[root@test-dhcp ~]# echo "{}" |jq -r type
object
[root@test-dhcp ~]# echo '[0, false, [], {}, null, "hello"]' |jq 'map(type)'
[
  "number",
  "boolean",
  "array",
  "object",
  "null",
  "string"
]

1. 查询数组中的值

[root@test-dhcp ~]# echo [1,2,3] |jq .[1]
2
[root@test-dhcp ~]# echo [1,2,3] |jq .[2]
3

1. 查询数组长度

[root@test-dhcp ~]# echo [1,2,3,9] |jq '.|length'
4
[root@test-dhcp ~]# echo [1,2,3] |jq '.|length'
3

1. 数组相加

[root@test-dhcp ~]# echo [1,2,3] |jq '. + [4,5,6]'
[
  1,
  2,
  3,
  4,
  5,
  6
]

1. 高级查询

[root@test-dhcp ~]# echo [1,2,3] | jq 'map(select(. >= 2))'
[
  2,
  3
]
[root@test-dhcp ~]# echo [1,2,3] | jq 'map(select(. == 2))'
[
  2
]
[root@test-dhcp ~]# echo [1,2,3] | jq 'map(select(. != 2))'
[
  1,
  3
]
[root@test-dhcp ~]# cat test.json 
[
  {
    "id": "0",
    "model": "Intel(R)Xeon(R)CPUE5-2620v4@2.10GHz"
  },
  {
    "id": "1",
    "model": "Intel(R)Xeon(R)CPUE5-2620v4@2.10GHz"
  }
]
[root@test-dhcp ~]# cat test.json |jq .[].model
"Intel(R)Xeon(R)CPUE5-2620v4@2.10GHz"
"Intel(R)Xeon(R)CPUE5-2620v4@2.10GHz"

1. 类型转换

[root@test-dhcp ~]# echo '["a","b,c,d","e"]' |jq 'join(",")'
"a,b,c,d,e"
[root@test-dhcp ~]# echo '["a","b,c,d","e",1]' |jq 'join(",")'
jq: error (at <stdin>:1): string (",") and number (1) cannot be added
[root@test-dhcp ~]# cat test.json 
liuxin,30,male
jiaweiqiang,29,femal
[root@test-dhcp ~]# jq -R 'split(",")|{"name":.[0],"age":.[1],"sex":.[2]}' ./test.json 
{
  "name": "liuxin",
  "age": "30",
  "sex": "male"
}
{
  "name": "jiaweiqiang",
  "age": "29",
  "sex": "femal"
}
[root@test-dhcp ~]# cat test.json 
{
  "name": "liuxin",
  "age": "30",
  "sex": "male"
}
{
  "name": "jiaweiqiang",
  "age": "29",
  "sex": "femal"
}
[root@test-dhcp ~]# cat test.json |jq . -c
{"name":"liuxin","age":"30","sex":"male"}
{"name":"jiaweiqiang","age":"29","sex":"femal"}

3. 总结

我之前写过一个抓取服务器硬件信息的shell脚本，在处理这些抓取到的数据时，使用jq工具很方便。总体来看这个工具还是很不错的。

更全面，更详细的介绍可登录官网学习。

参考网址：https://stedolan.github.io/jq/manual/