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25 <div id="preamble"><h1>Apache Module mod_substitute</h1>
27 <p><span>Available Languages: </span><a href="../en/mod/mod_substitute.html" title="English"> en </a></p>
29 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Perform search and replace operations on response bodies</td></tr>
30 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
31 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>substitute_module</td></tr>
32 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_substitute.c</td></tr>
33 <tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache HTTP Server 2.2.7 and later</td></tr></table>
36 <p><code class="module"><a href="../mod/mod_substitute.html">mod_substitute</a></code> provides a mechanism to perform
37 both regular expression and fixed string substitutions on
40 <div id="quickview"><h3 class="directives">Directives</h3>
42 <li><img alt="" src="../images/down.gif" /> <a href="#substitute">Substitute</a></li>
44 <ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
46 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
47 <div class="directive-section"><h2><a name="Substitute" id="Substitute">Substitute</a> <a name="substitute" id="substitute">Directive</a></h2>
48 <table class="directive">
49 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Pattern to filter the response content</td></tr>
50 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Substitute <var>s/pattern/substitution/[infq]</var></code></td></tr>
51 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
52 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
53 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
54 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_substitute</td></tr>
56 <p>The <code class="directive">Substitute</code> directive specifies a
57 search and replace pattern to apply to the response body.</p>
59 <p>The meaning of the pattern can be modified by using any
60 combination of these flags:</p>
63 <dt><code>i</code></dt>
64 <dd>Perform a case-insensitive match.</dd>
65 <dt><code>n</code></dt>
66 <dd>By default the pattern is treated as a regular expression.
67 Using the <code>n</code> flag forces the pattern to be treated
68 as a fixed string.</dd>
69 <dt><code>f</code></dt>
70 <dd>The <code>f</code> flag causes mod_substitute to flatten the
71 result of a substitution allowing for later substitutions to
72 take place on the boundary of this one. This is the default.</dd>
73 <dt><code>q</code></dt>
74 <dd>The <code>q</code> flag causes mod_substitute to not
75 flatten the buckets after each substitution. This can
76 result in much faster response and a decrease in memory
77 utilization, but should only be used if there is no possibility
78 that the result of one substitution will ever match a pattern
79 or regex of a subsequent one.</dd>
82 <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
84 AddOutputFilterByType SUBSTITUTE text/html
85 Substitute s/foo/bar/ni
90 <p>If either the pattern or the substitution contain a slash
91 character then an alternative delimiter should be used:</p>
93 <div class="example"><h3>Example of using an alternate delimiter</h3><pre class="prettyprint lang-config">
95 AddOutputFilterByType SUBSTITUTE text/html
96 Substitute "s|<BR */?>|<br />|i"
101 <p>Backreferences can be used in the comparison and in the substitution,
102 when regular expressions are used, as illustrated in the following example: </p>
103 <div class="example"><h3>Example of using backreferences and captures</h3><pre class="prettyprint lang-config">
105 AddOutputFilterByType SUBSTITUTE text/html
106 # "foo=k,bar=k" -> "foo/bar=k"
107 Substitute "s|foo=(\w+),bar=\1|foo/bar=$1"
112 <p>A common use scenario for <code>mod_substitute</code> is the
113 situation in which a front-end server proxies requests to a back-end
114 server which returns HTML with hard-coded embedded URLs that refer
115 to the back-end server. These URLs don't work for the end-user,
116 since the back-end server is unreachable.</p>
118 <p>In this case, <code>mod_substutite</code> can be used to rewrite
119 those URLs into something that will work from the front end:</p>
121 <div class="example"><h3>Rewriting URLs embedded in proxied content</h3><pre class="prettyprint lang-config">
122 ProxyPass /blog/ http://internal.blog.example.com
123 ProxyPassReverse /blog/ http://internal.blog.example.com/
125 Substitute "s|http://internal.blog.example.com/|http://www.example.com/blog/|i"
129 <p><code class="directive"><a href="../mod/mod_proxy.html#proxypassreverse">ProxyPassReverse</a></code>
130 modifies any <code>Location</code> (redirect) headers that are sent
131 by the back-end server, and, in this example,
132 <code>Substitute</code> takes care of the rest of the problem by
133 fixing up the HTML response as well.</p>
138 <div class="bottomlang">
139 <p><span>Available Languages: </span><a href="../en/mod/mod_substitute.html" title="English"> en </a></p>
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