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substitutions: String substitutions module for nginx

Installation

CentOS/RHEL 6, 7, 8 or Amazon Linux 2

yum -y install https://extras.getpagespeed.com/release-latest.rpm
yum -y install nginx-module-substitutions

Enable the module by adding the following at the top of /etc/nginx/nginx.conf:

load_module modules/ngx_http_subs_filter_module.so;

This document describes nginx-module-substitutions v0.6.5 released on May 28 2020.


nginx_substitutions_filter Note: this module is not distributed with the Nginx source. Installation instructions can be found below.

Description nginx_substitutions_filter is a filter module which can do both regular expression and fixed string substitutions on response bodies. This module is quite different from the Nginx's native Substitution Module. It scans the output chains buffer and matches string line by line, just like Apache's mod_substitute (http://httpd.apache.org/docs/trunk/mod/mod_substitute.html).

Example location / {

    subs_filter_types text/html text/css text/xml;
    subs_filter st(\d*).example.com $1.example.com ir;
    subs_filter a.example.com s.example.com;
    subs_filter http://$host https://$host;
}

Directives * subs_filter_types

*   subs_filter

subs_filter_types syntax: *subs_filter_types mime-type [mime-types] *

default: *subs_filter_types text/html*

context: *http, server, location*

*subs_filter_types* is used to specify which content types should be
checked for *subs_filter*, in addition to *text/html*. The default is
only *text/html*.

This module just works with plain text. If the response is compressed,
it can't uncompress the response and will ignore this response. This
module can be compatible with gzip filter module. But it will not work
with proxy compressed response. You can disable the compressed response
like this:

proxy_set_header Accept-Encoding "";

subs_filter syntax: *subs_filter source_str destination_str [gior] *

default: *none*

context: *http, server, location*

*subs_filter* allows replacing source string(regular expression or
fixed) in the nginx response with destination string. The variables 
in matching text is only avaiable under fixed string mode, which means 
the matching text could not contain variables if it is a regular 
expression. Substitution text may contain variables. More than one 
substitution rules per location is supported. 
The meaning of the third flags are:

*   *g*(default): Replace all the match strings.

*   *i*: Perform a case-insensitive match.

*   *o*: Just replace the first one.

*   *r*: The pattern is treated as a regular expression, default is
    fixed string.

subs_filter_bypass syntax: subs_filter_bypass $variable1 ...

default: *none*

context: *http, server, location*

You can sepcify several variables with this directive. If at least one
of the variable is not empty and is not equal to '0', this substitution
filter will be disabled.

Installation To install, get the source with subversion:

git clone
git://github.com/yaoweibin/ngx_http_substitutions_filter_module.git

and then compile nginx with the following option:

./configure --add-module=/path/to/module

Known issue * Can't substitute the response header.

CHANGES Changes with nginx_substitutions_filter 0.6.4 2014-02-15

*   Now non-200 response will work

*   added the subs_filter_bypass directive

Changes with nginx_substitutions_filter 0.6.2 2012-08-26

*   fixed a bug of buffer overlap

*   fixed a bug with last zero buffer

Changes with nginx_substitutions_filter 0.6.0 2012-06-30

*   refactor this module

Changes with nginx_substitutions_filter 0.5.2 2010-08-11

*   do many optimizing for this module

*   fix a bug of buffer overlap

*   fix a segment fault bug when output chain return NGX_AGAIN.

*   fix a bug about last buffer with no linefeed. This may cause segment
    fault. Thanks for Josef Fröhle

Changes with nginx_substitutions_filter 0.5 2010-04-15

*   refactor the source structure, create branches of dev

*   fix a bug of small chunk of buffers causing lose content

*   fix the bug of last_buf and the nginx's compatibility above 0.8.25

*   fix a bug with unwanted capture config error in fix string
    substitution

*   add feature of regex captures

Changes with nginx_substitutions_filter 0.4 2009-12-23

*   fix many bugs

Changes with nginx_substitutions_filter 0.3 2009-02-04

*   Initial public release

Reporting a bug Questions/patches may be directed to Weibin Yao, yaoweibin@gmail.com.

Copyright & License This module is licensed under the BSD license.

Copyright (C) 2014 by Weibin Yao <yaoweibin@gmail.com>.

All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

*
      Redistributions of source code must retain the above copyright

    notice, this list of conditions and the following disclaimer.

*
      Redistributions in binary form must reproduce the above copyright

    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

GitHub

You may find additional configuration tips and documentation for this module in the GitHub repository for nginx-module-substitutions.