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  10 <title>mod_substitute - Apache HTTP Server Version 2.5</title>
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  21 <p class="apache">Apache HTTP Server Version 2.5</p>
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  27 <div id="preamble"><h1>Apache Module mod_substitute</h1>
  28 <div class="toplang">
  29 <p><span>Available Languages: </span><a href="../en/mod/mod_substitute.html" title="English">&nbsp;en&nbsp;</a></p>
  30 </div>
  31 <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>
  32 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
  33 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>substitute_module</td></tr>
  34 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_substitute.c</td></tr></table>
  35 <h3>Summary</h3>
  36
  37     <p><code class="module"><a href="../mod/mod_substitute.html">mod_substitute</a></code> provides a mechanism to perform
  38     both regular expression and fixed string substitutions on
  39     response bodies.</p>
  40 </div>
  41 <div id="quickview"><h3 class="directives">Directives</h3>
  42 <ul id="toc">
  43 <li><img alt="" src="../images/down.gif" /> <a href="#substitute">Substitute</a></li>
  44 <li><img alt="" src="../images/down.gif" /> <a href="#substitutemaxlinelength">SubstituteMaxLineLength</a></li>
  45 </ul>
  46 <ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
  47
  48 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  49 <div class="directive-section"><h2><a name="Substitute" id="Substitute">Substitute</a> <a name="substitute" id="substitute">Directive</a></h2>
  50 <table class="directive">
  51 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Pattern to filter the response content</td></tr>
  52 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Substitute <var>s/pattern/substitution/[infq]</var></code></td></tr>
  53 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
  54 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
  55 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
  56 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_substitute</td></tr>
  57 </table>
  58     <p>The <code class="directive">Substitute</code> directive specifies a
  59     search and replace pattern to apply to the response body.</p>
  60
  61     <p>The meaning of the pattern can be modified by using any
  62     combination of these flags:</p>
  63
  64     <dl>
  65         <dt><code>i</code></dt>
  66         <dd>Perform a case-insensitive match.</dd>
  67         <dt><code>n</code></dt>
  68         <dd>By default the pattern is treated as a regular expression.
  69         Using the <code>n</code> flag forces the pattern to be treated
  70         as a fixed string.</dd>
  71         <dt><code>f</code></dt>
  72         <dd>The <code>f</code> flag causes mod_substitute to flatten the
  73         result of a substitution allowing for later substitutions to
  74         take place on the boundary of this one. This is the default.</dd>
  75         <dt><code>q</code></dt>
  76         <dd>The <code>q</code> flag causes mod_substitute to not
  77         flatten the buckets after each substitution. This can
  78         result in much faster response and a decrease in memory
  79         utilization, but should only be used if there is no possibility
  80         that the result of one substitution will ever match a pattern
  81         or regex of a subsequent one.</dd>
  82     </dl>
  83
  84     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">&lt;Location "/"&gt;
  85     AddOutputFilterByType SUBSTITUTE text/html
  86     Substitute s/foo/bar/ni
  87 &lt;/Location&gt;</pre>
  88 </div>
  89
  90     <p>If either the pattern or the substitution contain a slash
  91     character then an alternative delimiter should be used:</p>
  92
  93     <div class="example"><h3>Example of using an alternate delimiter</h3><pre class="prettyprint lang-config">&lt;Location "/"&gt;
  94     AddOutputFilterByType SUBSTITUTE text/html
  95     Substitute "s|&lt;BR */?&gt;|&lt;br /&gt;|i"
  96 &lt;/Location&gt;</pre>
  97 </div>
  98
  99     <p>Backreferences can be used in the comparison and in the substitution,
 100     when regular expressions are used, as illustrated in the following example: </p>
 101     <div class="example"><h3>Example of using backreferences and captures</h3><pre class="prettyprint lang-config">&lt;Location "/"&gt;
 102     AddOutputFilterByType SUBSTITUTE text/html
 103     # "foo=k,bar=k" -&gt; "foo/bar=k"
 104     Substitute "s|foo=(\w+),bar=\1|foo/bar=$1"
 105 &lt;/Location&gt;</pre>
 106 </div>
 107
 108     <p>A common use scenario for <code>mod_substitute</code> is the
 109     situation in which a front-end server proxies requests to a back-end
 110     server which returns HTML with hard-coded embedded URLs that refer
 111     to the back-end server. These URLs don't work for the end-user,
 112     since the back-end server is unreachable.</p>
 113
 114     <p>In this case, <code>mod_substutite</code> can be used to rewrite
 115     those URLs into something that will work from the front end:</p>
 116
 117     <div class="example"><h3>Rewriting URLs embedded in proxied content</h3><pre class="prettyprint lang-config">ProxyPass        "/blog/" "http://internal.blog.example.com"
 118 ProxyPassReverse "/blog/" "http://internal.blog.example.com/"
 119
 120 Substitute "s|http://internal.blog.example.com/|http://www.example.com/blog/|i"</pre>
 121 </div>
 122
 123     <p><code class="directive"><a href="../mod/mod_proxy.html#proxypassreverse">ProxyPassReverse</a></code>
 124     modifies any <code>Location</code> (redirect) headers that are sent
 125     by the back-end server, and, in this example,
 126     <code>Substitute</code> takes care of the rest of the problem by
 127     fixing up the HTML response as well.</p>
 128
 129
 130 </div>
 131 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 132 <div class="directive-section"><h2><a name="SubstituteMaxLineLength" id="SubstituteMaxLineLength">SubstituteMaxLineLength</a> <a name="substitutemaxlinelength" id="substitutemaxlinelength">Directive</a></h2>
 133 <table class="directive">
 134 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Set the maximum line size</td></tr>
 135 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SubstituteMaxLineLength <var>bytes</var>(b|B|k|K|m|M|g|G)</code></td></tr>
 136 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>SubstituteMaxLineLength 1m</code></td></tr>
 137 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
 138 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
 139 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 140 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_substitute</td></tr>
 141 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in httpd 2.4.11 and later</td></tr>
 142 </table>
 143     <p>The maximum line size handled by <code class="module"><a href="../mod/mod_substitute.html">mod_substitute</a></code>
 144     is limited to restrict memory use. The limit can be configured
 145     using <code class="directive">SubstituteMaxLineLength</code>.
 146     The value can be given as the number of bytes and can be suffixed
 147     with a single letter <code>b</code>, <code>B</code>, <code>k</code>,
 148     <code>K</code>, <code>m</code>, <code>M</code>, <code>g</code>,
 149     <code>G</code> to provide the size in bytes, kilobytes, megabytes
 150     or gigabytes respectively.</p>
 151
 152     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">&lt;Location "/"&gt;
 153     AddOutputFilterByType SUBSTITUTE text/html
 154     SubstituteMaxLineLength 10m
 155     Substitute s/foo/bar/ni
 156 &lt;/Location&gt;</pre>
 157 </div>
 158
 159
 160 </div>
 161 </div>
 162 <div class="bottomlang">
 163 <p><span>Available Languages: </span><a href="../en/mod/mod_substitute.html" title="English">&nbsp;en&nbsp;</a></p>
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