Apache HTTP Server Version 2.4
Description: | Perform search and replace operations on response bodies |
---|---|
Status: | Extension |
Module Identifier: | substitute_module |
Source File: | mod_substitute.c |
Compatibility: | Available in Apache HTTP Server 2.2.7 and later |
mod_substitute
provides a mechanism to perform
both regular expression and fixed string substitutions on
response bodies.
Description: | Pattern to filter the response content |
---|---|
Syntax: | Substitute s/pattern/substitution/[infq] |
Context: | directory, .htaccess |
Override: | FileInfo |
Status: | Extension |
Module: | mod_substitute |
The Substitute
directive specifies a
search and replace pattern to apply to the response body.
The meaning of the pattern can be modified by using any combination of these flags:
i
n
n
flag forces the pattern to be treated
as a fixed string.f
f
flag causes mod_substitute
to flatten the
result of a substitution allowing for later substitutions to
take place on the boundary of this one. This is the default.q
q
flag causes mod_substitute
to not
flatten the buckets after each substitution. This can
result in much faster response and a decrease in memory
utilization, but should only be used if there is no possibility
that the result of one substitution will ever match a pattern
or regex of a subsequent one.<Location "/"> AddOutputFilterByType SUBSTITUTE text/html Substitute "s/foo/bar/ni" </Location>
If either the pattern or the substitution contain a slash character then an alternative delimiter should be used:
<Location "/"> AddOutputFilterByType SUBSTITUTE text/html Substitute "s|<BR */?>|<br />|i" </Location>
Backreferences can be used in the comparison and in the substitution, when regular expressions are used, as illustrated in the following example:
<Location "/"> AddOutputFilterByType SUBSTITUTE text/html # "foo=k,bar=k" -> "foo/bar=k" Substitute "s|foo=(\w+),bar=\1|foo/bar=$1" </Location>
A common use scenario for mod_substitute
is the
situation in which a front-end server proxies requests to a back-end
server which returns HTML with hard-coded embedded URLs that refer
to the back-end server. These URLs don't work for the end-user,
since the back-end server is unreachable.
In this case, mod_substitute
can be used to rewrite
those URLs into something that will work from the front end:
ProxyPass "/blog/" "http://internal.blog.example.com" ProxyPassReverse "/blog/" "http://internal.blog.example.com/" Substitute "s|http://internal.blog.example.com/|http://www.example.com/blog/|i"
ProxyPassReverse
modifies any Location
(redirect) headers that are sent
by the back-end server, and, in this example,
Substitute
takes care of the rest of the problem by
fixing up the HTML response as well.
Description: | Change the merge order of inherited patterns |
---|---|
Syntax: | SubstituteInheritBefore on|off |
Default: | SubstituteInheritBefore off |
Context: | directory, .htaccess |
Override: | FileInfo |
Status: | Extension |
Module: | mod_substitute |
Compatibility: | Available in httpd 2.4.17 and later |
Whether to apply the inherited Substitute
patterns first (on
), or after the ones of the current
context (off
).
SubstituteInheritBefore
is itself inherited,
hence contexts that inherit it (those that don't specify their own
SubstituteInheritBefore
value) will apply the
closest defined merge order.
Description: | Set the maximum line size |
---|---|
Syntax: | SubstituteMaxLineLength bytes(b|B|k|K|m|M|g|G) |
Default: | SubstituteMaxLineLength 1m |
Context: | directory, .htaccess |
Override: | FileInfo |
Status: | Extension |
Module: | mod_substitute |
Compatibility: | Available in httpd 2.4.11 and later |
The maximum line size handled by mod_substitute
is limited to restrict memory use. The limit can be configured
using SubstituteMaxLineLength
.
The value can be given as the number of bytes and can be suffixed
with a single letter b
, B
, k
,
K
, m
, M
, g
,
G
to provide the size in bytes, kilobytes, megabytes
or gigabytes respectively.
<Location "/"> AddOutputFilterByType SUBSTITUTE text/html SubstituteMaxLineLength 10m Substitute "s/foo/bar/ni" </Location>