Linux之jq

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

系统环境：centos 7

一、安装

（1）yum安装

a、安装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   ###检查是否已经添加到源列表

b、yum install -y jq

（2）源码安装

a、下载源码包

#  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

编译安装完成以后就能在该目录下看见jq二进制文件了，添加到环境变量~/.bashrc

如图：

# source ~/.bashrc    

安装完成，现在就可以使用jq命令

二、jq测试

（1）简单测试

#  echo '{"yjt":"boy","age":20}' |jq .   #注意，命令最后有一个点，代表显示全部的json文件

效果：

注意：jq命令会检查json格式的合法性，如果不合法，将保错，具体的json格式，请浏览：http://www.w3school.com.cn/json/json_syntax.asp 或者 https://stedolan.github.io/jq/manual/

 （2）通过key获取值，如何获取呢？  

jq '.key'

file文件内容

{
"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）获取不存在的key会返回null

（4）嵌套解析

（5）内建函数

a、has  用来判断是否存在某个key

b、key  用来获取json中的key元素的

例：