什么是jq？jq是Linux下面把文本字符串格式化成json格式的工具
系統環境：centos 7
一、安裝
（1）yum安裝
a、安裝epel源
# wget http://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
# rpm -ivh epel-release-latest-7.noarch.rpm
# yum repolist ###檢查是否已經添加到源列表
b、yum install -y jq
（2）源碼安裝
a、下載源碼包
# wget https://github.com/stedolan/jq/releases/download/jq-1.5/jq-1.5.tar.gz
# tar zxvf jq-1.5.tar.gz
# cd jq-1.5
# ./configure
# make && make install
編譯安裝完成以后就能在該目錄下看見jq二進制文件了，添加到環境變量~/.bashrc
如圖：
# source ~/.bashrc
安裝完成，現在就可以使用jq命令
二、jq測試
（1）簡單測試
# echo '{"yjt":"boy","age":20}' |jq . #注意，命令最后有一個點，代表顯示全部的json文件
效果：
注意：jq命令會檢查json格式的合法性，如果不合法，將保錯，具體的json格式，請瀏覽：http://www.w3school.com.cn/json/json_syntax.asp 或者 https://stedolan.github.io/jq/manual/
（2）通過key獲取值，如何獲取呢？
jq '.key'
file文件內容
{
"System_Time":"2018-11-27 17:42:02",
"Hostname":"test.com",
"Network":[
{
"Network_Card": "bond1",
"ip":"10.126.140.16",
"Input_Traffic": "4.448K/S",
"Output_Traffic": "2.649K/S "
},{
"Network_Card": "eth4",
"ip":null,
"Input_Traffic": "2.679K/S",
"Output_Traffic": "1.805K/S "
},{
"Network_Card": "eth6",
"ip":null,
"Input_Traffic": "0.750K/S",
"Output_Traffic": "0.000K/S "
}],
"CPU":{
"us":"0%",
"sy":"0%",
"id":"100%",
"wa":"0%",
"cpu_rate":"0.01%",
"CPU_Load_Average": " 0.15, 0.04, 0.01",
"Running_Process":"1",
"Total_Process":"696",
"Host_Running_Time":" 18 days 22:53",
"User_Connection_Number":"2" ,
"CPU_Status":"Normal"
},
"Memory":{
"total_mem":"128644M",
"use_mem": "1373M",
"free_mem": "127270M",
"use_rate": "1%",
"free_swap": "65535M",
"total_swap": "65535M",
"use_swap": "0M",
"swap_use_rate": "0%",
"Memory_Status":"Normal",
"Swap_Memory_Status":"Normal"
},
"disk":{
"root_use":"1%",
"root_status":"Normal",
"var_use":"1%",
"vae_status":"Normal",
"data_use":"1%",
"data_status":"Normal",
"data1_use":"0%",
"data1_status":"Normal",
"data2_use":"1%",
"data2_status":"Normal",
"data3_use":"1%",
"data3_status":"Normal"
},
"TCP":{
"TIME_WAIT":"36",
"FIN_WAIT1":"0",
"FIN_WAIT2":"0",
"CLOSE_WAIT":"0",
"ESTABLISHED":"2",
"SYN_RECV":"0",
"LAST_ACKV":"0",
"CLOSING":"0"
},
"type":"END"
}
例：
（3）獲取不存在的key會返回null
（4）嵌套解析
（5）內建函數
a、has 用來判斷是否存在某個key
b、key 用來獲取json中的key元素的
例：
