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  10 <title>mod_substitute - Apache HTTP Server Version 2.5</title>
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  20 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/quickreference.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
  21 <p class="apache">Apache HTTP Server Version 2.5</p>
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  25 <a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.5</a> &gt; <a href="./">Modules</a></div>
  26 <div id="page-content">
  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> |
  30 <a href="../fr/mod/mod_substitute.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a></p>
  31 </div>
  32 <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>
  33 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
  34 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>substitute_module</td></tr>
  35 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_substitute.c</td></tr></table>
  36 <h3>Summary</h3>
  37
  38     <p><code class="module"><a href="../mod/mod_substitute.html">mod_substitute</a></code> provides a mechanism to perform
  39     both regular expression and fixed string substitutions on
  40     response bodies.</p>
  41 </div>
  42 <div id="quickview"><h3 class="directives">Directives</h3>
  43 <ul id="toc">
  44 <li><img alt="" src="../images/down.gif" /> <a href="#substitute">Substitute</a></li>
  45 <li><img alt="" src="../images/down.gif" /> <a href="#substituteinheritbefore">SubstituteInheritBefore</a></li>
  46 <li><img alt="" src="../images/down.gif" /> <a href="#substitutemaxlinelength">SubstituteMaxLineLength</a></li>
  47 </ul>
  48 <h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&amp;list_id=144532&amp;product=Apache%20httpd-2&amp;query_format=specific&amp;order=changeddate%20DESC%2Cpriority%2Cbug_severity&amp;component=mod_substitute">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&amp;component=mod_substitute">Report a bug</a></li></ul><h3>See also</h3>
  49 <ul class="seealso">
  50 <li><a href="#comments_section">Comments</a></li></ul></div>
  51
  52 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  53 <div class="directive-section"><h2><a name="Substitute" id="Substitute">Substitute</a> <a name="substitute" id="substitute">Directive</a></h2>
  54 <table class="directive">
  55 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Pattern to filter the response content</td></tr>
  56 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Substitute <var>s/pattern/substitution/[infq]</var></code></td></tr>
  57 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
  58 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
  59 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
  60 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_substitute</td></tr>
  61 </table>
  62     <p>The <code class="directive">Substitute</code> directive specifies a
  63     search and replace pattern to apply to the response body.</p>
  64
  65     <p>The meaning of the pattern can be modified by using any
  66     combination of these flags:</p>
  67
  68     <dl>
  69         <dt><code>i</code></dt>
  70         <dd>Perform a case-insensitive match.</dd>
  71         <dt><code>n</code></dt>
  72         <dd>By default the pattern is treated as a regular expression.
  73         Using the <code>n</code> flag forces the pattern to be treated
  74         as a fixed string.</dd>
  75         <dt><code>f</code></dt>
  76         <dd>The <code>f</code> flag causes <code>mod_substitute</code> to flatten the
  77         result of a substitution allowing for later substitutions to
  78         take place on the boundary of this one. This is the default.</dd>
  79         <dt><code>q</code></dt>
  80         <dd>The <code>q</code> flag causes <code>mod_substitute</code> to not
  81         flatten the buckets after each substitution. This can
  82         result in much faster response and a decrease in memory
  83         utilization, but should only be used if there is no possibility
  84         that the result of one substitution will ever match a pattern
  85         or regex of a subsequent one.</dd>
  86     </dl>
  87
  88     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">&lt;Location "/"&gt;
  89     AddOutputFilterByType SUBSTITUTE text/html
  90     Substitute "s/foo/bar/ni"
  91 &lt;/Location&gt;</pre>
  92 </div>
  93
  94     <p>If either the pattern or the substitution contain a slash
  95     character then an alternative delimiter should be used:</p>
  96
  97     <div class="example"><h3>Example of using an alternate delimiter</h3><pre class="prettyprint lang-config">&lt;Location "/"&gt;
  98     AddOutputFilterByType SUBSTITUTE text/html
  99     Substitute "s|&lt;BR */?&gt;|&lt;br /&gt;|i"
 100 &lt;/Location&gt;</pre>
 101 </div>
 102
 103     <p>Backreferences can be used in the comparison and in the substitution,
 104     when regular expressions are used, as illustrated in the following example: </p>
 105     <div class="example"><h3>Example of using backreferences and captures</h3><pre class="prettyprint lang-config">&lt;Location "/"&gt;
 106     AddOutputFilterByType SUBSTITUTE text/html
 107     # "foo=k,bar=k" -&gt; "foo/bar=k"
 108     Substitute "s|foo=(\w+),bar=\1|foo/bar=$1"
 109 &lt;/Location&gt;</pre>
 110 </div>
 111
 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>
 117
 118     <p>In this case, <code>mod_substitute</code> can be used to rewrite
 119     those URLs into something that will work from the front end:</p>
 120
 121     <div class="example"><h3>Rewriting URLs embedded in proxied content</h3><pre class="prettyprint lang-config">ProxyPass        "/blog/" "http://internal.blog.example.com"
 122 ProxyPassReverse "/blog/" "http://internal.blog.example.com/"
 123
 124 Substitute "s|http://internal.blog.example.com/|http://www.example.com/blog/|i"</pre>
 125 </div>
 126
 127     <p><code class="directive"><a href="../mod/mod_proxy.html#proxypassreverse">ProxyPassReverse</a></code>
 128     modifies any <code>Location</code> (redirect) headers that are sent
 129     by the back-end server, and, in this example,
 130     <code class="directive">Substitute</code> takes care of the rest of the problem by
 131     fixing up the HTML response as well.</p>
 132
 133
 134 </div>
 135 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 136 <div class="directive-section"><h2><a name="SubstituteInheritBefore" id="SubstituteInheritBefore">SubstituteInheritBefore</a> <a name="substituteinheritbefore" id="substituteinheritbefore">Directive</a></h2>
 137 <table class="directive">
 138 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Change the merge order of inherited patterns</td></tr>
 139 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SubstituteInheritBefore on|off</code></td></tr>
 140 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>SubstituteInheritBefore on</code></td></tr>
 141 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
 142 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
 143 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 144 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_substitute</td></tr>
 145 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in httpd 2.4.17 and later</td></tr>
 146 </table>
 147     <p>Whether to apply the inherited <code class="directive"><a href="#substitute">Substitute</a></code>
 148     patterns first (<code>on</code>), or after the ones of the current
 149     context (<code>off</code>).
 150     The latter was the default in versions 2.4 and earlier, but changed
 151     starting with 2.5, hence <code class="directive">SubstituteInheritBefore</code>
 152     set to <code>off</code> allows to restore the legacy behaviour.
 153     <code class="directive">SubstituteInheritBefore</code> is itself inherited,
 154     hence contexts that inherit it (those that don't specify their own
 155     <code class="directive">SubstituteInheritBefore</code> value) will apply the
 156     closest defined merge order.</p>
 157
 158 </div>
 159 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 160 <div class="directive-section"><h2><a name="SubstituteMaxLineLength" id="SubstituteMaxLineLength">SubstituteMaxLineLength</a> <a name="substitutemaxlinelength" id="substitutemaxlinelength">Directive</a></h2>
 161 <table class="directive">
 162 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Set the maximum line size</td></tr>
 163 <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>
 164 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>SubstituteMaxLineLength 1m</code></td></tr>
 165 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
 166 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
 167 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 168 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_substitute</td></tr>
 169 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in httpd 2.4.11 and later</td></tr>
 170 </table>
 171     <p>The maximum line size handled by <code class="module"><a href="../mod/mod_substitute.html">mod_substitute</a></code>
 172     is limited to restrict memory use. The limit can be configured
 173     using <code class="directive">SubstituteMaxLineLength</code>.
 174     The value can be given as the number of bytes and can be suffixed
 175     with a single letter <code>b</code>, <code>B</code>, <code>k</code>,
 176     <code>K</code>, <code>m</code>, <code>M</code>, <code>g</code>,
 177     <code>G</code> to provide the size in bytes, kilobytes, megabytes
 178     or gigabytes respectively.</p>
 179
 180     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">&lt;Location "/"&gt;
 181     AddOutputFilterByType SUBSTITUTE text/html
 182     SubstituteMaxLineLength 10m
 183     Substitute "s/foo/bar/ni"
 184 &lt;/Location&gt;</pre>
 185 </div>
 186
 187
 188 </div>
 189 </div>
 190 <div class="bottomlang">
 191 <p><span>Available Languages: </span><a href="../en/mod/mod_substitute.html" title="English">&nbsp;en&nbsp;</a> |
 192 <a href="../fr/mod/mod_substitute.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a></p>
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