# 替换响应内容

## http\_sub\_module

对http响应内容的替换。

```nginx
# 针对指定内容进行替换，将string替换为replacement
Syntax: sub_filter string replacement;
Default:
Context: http, server, location

# 指定匹配方式，匹配以此还是每个都匹配，默认匹配一次
Syntax: sub_filter_once on | off;
Default: sub_filter_once on;
Context: http, server, location

# nginx服务端与客户端，进行每次请求时校验服务端的内容是否发生变化
# last_modified 记录了时间，判断服务端数据是否更新，从而保证数据最新，常用于缓存场景
Syntax: sub_filter_last_modified on | off;
Default: sub_filter_last_modified off;
Context: http, server, location
```

**实例：**

```nginx
location / {
    root html;
	# 所有都替换
    sub_filter_once off;
    # 将所有hello 替换为 HELLO
    sub_filter 'hello' 'HELLO';
}
```


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