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本文主要针对nginx的ngx_http_sub_module模块做简单介绍，本文具体包括如下指令：sub_filter,sub_filter_once,sub_filter_types
该ngx_http_sub_module模块是一个过滤器，通过使用特定的字符串替换另外一个字符串来改变相应。
这个模块是不是默认内建模块，它应--with-http_sub_module参数启用。
配置示例
location / {
sub_filter </head>
'</head><script language="javascript" src="$script"></script>';
sub_filter_once on;
}
Nginx原文：
The ngx_http_sub_module module is a filter that modifies a response by replacing one specified string by another.
This module is not built by default, it should be enabled with the --with-http_sub_module configuration parameter.
Example Configuration
location / {
sub_filter </head>
'</head><script language="javascript" src="$script"></script>';
sub_filter_once on;
}
1. sub_filter
| syntax: | sub_filter string replacement; |
| default: | — |
| context: | http, server, location |
设置一个需要被改变的字符串以及一个用来替换的字符串。字符串的替换工作忽略大小写。替换字符串能包括变量
Nginx原文：
Sets a string that needs to be changed, and a replacement string. The string to be replaced is matched ignoring the case. A replacement string can contain variables.
2. sub_filter_once
| syntax: | sub_filter_once on | off; |
| default: | sub_filter_once on; |
| context: | http, server, location |
确定字符串应该被替换多少次， 一次， 还是多次
Nginx原文：
Determines how many times to look for a string to be replaced, once or several times.
3. sub_filter_types
| syntax: | sub_filter_types mime-type...; |
| default: | sub_filter_types text/html; |
| context: | http, server, location |
设置字符串替换功能在那些MIME类型的相应中有效， 除了在“text/html”相应中。 特殊的“*”将匹配任意类型的MIME类型。
Nginx原文：
Enables string replacement in responses with the specified MIME types in addition to “text/html”. The special value “*” matches any MIME type (0.8.29).
