# 命令host

常用的分析域名查询工具。

**host命令** 是常用的分析域名查询工具，可以用来测试域名系统工作是否正常。

## 安装

如果系统找不到该命令，那么就是没有安装过 `bind-utils` 软件工具包，下面安装一下就好。

```bash
#CentOS
yum install -y bind-utils

#Ubuntu
sudo apt install bind-utils
```

`bind-utils` 软件包包含：bind测试工具、dig 域名解析工具、host 域名和IP互查和nslookup 交互式DNS查询等等。

## 语法

```bash
host (选项) (参数)
```

## 选项

```bash
-a：显示详细的DNS信息；
-c<类型>：指定查询类型，默认值为“IN“；
-C：查询指定主机的完整的SOA记录；
-r：在查询域名时，不使用递归的查询方式；
-t<类型>：指定查询的域名信息类型；
-v：显示指令执行的详细信息；
-w：如果域名服务器没有给出应答信息，则总是等待，直到域名服务器给出应答；
-W<时间>：指定域名查询的最长时间，如果在指定时间内域名服务器没有给出应答信息，则退出指令；
-4：使用IPv4；
-6：使用IPv6.
```

## 参数

```bash
主机：指定要查询信息的主机信息。
```

## 实例

```bash
[root@localhost ~]# host www.jsdig.com 
www.jsdig.com is an alias for host.1.jsdig.com.
host.1.jsdig.com has address 100.42.212.8
[root@localhost ~]# host -a www.jsdig.com
Trying "www.jsdig.com"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34671
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;www.jsdig.com.               IN      ANY
;; ANSWER SECTION:
www.jsdig.com.        463     IN      CNAME   host.1.jsdig.com.
Received 54 bytes from 202.96.104.15#53 in 0 ms


host baidu.com
baidu.com has address 220.181.38.251
baidu.com has address 220.181.38.148
baidu.com mail is handled by 10 mx.maillb.baidu.com.
baidu.com mail is handled by 20 jpmx.baidu.com.
baidu.com mail is handled by 15 mx.n.shifen.com.
baidu.com mail is handled by 20 mx1.baidu.com.
baidu.com mail is handled by 20 mx50.baidu.com.
baidu.com mail is handled by 20 usmx01.baidu.com.
```


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