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| <div id="preamble"><h1>Apache Module mod_substitute</h1> |
| <div class="toplang"> |
| <p><span>Available Languages: </span><a href="../en/mod/mod_substitute.html" title="English"> en </a> | |
| <a href="../fr/mod/mod_substitute.html" hreflang="fr" rel="alternate" title="Français"> fr </a></p> |
| </div> |
| <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> |
| <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr> |
| <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>substitute_module</td></tr> |
| <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_substitute.c</td></tr> |
| <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> |
| <h3>Summary</h3> |
| |
| <p><code class="module"><a href="../mod/mod_substitute.html">mod_substitute</a></code> provides a mechanism to perform |
| both regular expression and fixed string substitutions on |
| response bodies.</p> |
| </div> |
| <div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><h3 class="directives">Directives</h3> |
| <ul id="toc"> |
| <li><img alt="" src="../images/down.gif" /> <a href="#substitute">Substitute</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#substituteinheritbefore">SubstituteInheritBefore</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#substitutemaxlinelength">SubstituteMaxLineLength</a></li> |
| </ul> |
| <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__&list_id=144532&product=Apache%20httpd-2&query_format=specific&order=changeddate%20DESC%2Cpriority%2Cbug_severity&component=mod_substitute">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&component=mod_substitute">Report a bug</a></li></ul><h3>See also</h3> |
| <ul class="seealso"> |
| <li><a href="#comments_section">Comments</a></li></ul></div> |
| |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="directive-section"><h2><a name="Substitute" id="Substitute">Substitute</a> <a name="substitute" id="substitute">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Pattern to filter the response content</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Substitute <var>s/pattern/substitution/[infq]</var></code></td></tr> |
| <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr> |
| <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr> |
| <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> |
| <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_substitute</td></tr> |
| </table> |
| <p>The <code class="directive">Substitute</code> directive specifies a |
| search and replace pattern to apply to the response body.</p> |
| |
| <p>The meaning of the pattern can be modified by using any |
| combination of these flags:</p> |
| |
| <dl> |
| <dt><code>i</code></dt> |
| <dd>Perform a case-insensitive match.</dd> |
| <dt><code>n</code></dt> |
| <dd>By default the pattern is treated as a regular expression. |
| Using the <code>n</code> flag forces the pattern to be treated |
| as a fixed string.</dd> |
| <dt><code>f</code></dt> |
| <dd>The <code>f</code> flag causes <code>mod_substitute</code> to flatten the |
| result of a substitution allowing for later substitutions to |
| take place on the boundary of this one. This is the default.</dd> |
| <dt><code>q</code></dt> |
| <dd>The <code>q</code> flag causes <code>mod_substitute</code> 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.</dd> |
| </dl> |
| |
| <p>The <var>substitution</var> may contain literal text and regular |
| expression backreferences</p> |
| |
| <div class="example"><h3>Example</h3><pre class="prettyprint lang-config"><Location "/"> |
| AddOutputFilterByType SUBSTITUTE text/html |
| Substitute "s/foo/bar/ni" |
| </Location></pre> |
| </div> |
| |
| <p>The character which is used to separate (or "delimit") the |
| various parts of the substitution string is referred to as the |
| "delimiter", and it is most common to use a slash for this |
| purpose.</p> |
| |
| <p>If either the pattern or the substitution contain a slash |
| character then an alternative delimiter may be used to make the |
| directive more readable:</p> |
| |
| <div class="example"><h3>Example of using an alternate delimiter</h3><pre class="prettyprint lang-config"><Location "/"> |
| AddOutputFilterByType SUBSTITUTE text/html |
| Substitute "s|<BR */?>|<br />|i" |
| </Location></pre> |
| </div> |
| |
| <p>Backreferences can be used in the comparison and in the substitution, |
| when regular expressions are used, as illustrated in the following example: </p> |
| <div class="example"><h3>Example of using backreferences and captures</h3><pre class="prettyprint lang-config"><Location "/"> |
| AddOutputFilterByType SUBSTITUTE text/html |
| # "foo=k,bar=k" -> "foo/bar=k" |
| Substitute "s|foo=(\w+),bar=\1|foo/bar=$1|" |
| </Location></pre> |
| </div> |
| |
| <p>A common use scenario for <code>mod_substitute</code> 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.</p> |
| |
| <p>In this case, <code>mod_substitute</code> can be used to rewrite |
| those URLs into something that will work from the front end:</p> |
| |
| <div class="example"><h3>Rewriting URLs embedded in proxied content</h3><pre class="prettyprint lang-config">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"</pre> |
| </div> |
| |
| <p><code class="directive"><a href="../mod/mod_proxy.html#proxypassreverse">ProxyPassReverse</a></code> |
| modifies any <code>Location</code> (redirect) headers that are sent |
| by the back-end server, and, in this example, |
| <code class="directive">Substitute</code> takes care of the rest of the problem by |
| fixing up the HTML response as well.</p> |
| |
| |
| </div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="directive-section"><h2><a name="SubstituteInheritBefore" id="SubstituteInheritBefore">SubstituteInheritBefore</a> <a name="substituteinheritbefore" id="substituteinheritbefore">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Change the merge order of inherited patterns</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SubstituteInheritBefore on|off</code></td></tr> |
| <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>SubstituteInheritBefore off</code></td></tr> |
| <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr> |
| <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr> |
| <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> |
| <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_substitute</td></tr> |
| <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in httpd 2.4.17 and later</td></tr> |
| </table> |
| <p>Whether to apply the inherited <code class="directive"><a href="#substitute">Substitute</a></code> |
| patterns first (<code>on</code>), or after the ones of the current |
| context (<code>off</code>). |
| <code class="directive">SubstituteInheritBefore</code> is itself inherited, |
| hence contexts that inherit it (those that don't specify their own |
| <code class="directive">SubstituteInheritBefore</code> value) will apply the |
| closest defined merge order.</p> |
| |
| </div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="directive-section"><h2><a name="SubstituteMaxLineLength" id="SubstituteMaxLineLength">SubstituteMaxLineLength</a> <a name="substitutemaxlinelength" id="substitutemaxlinelength">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Set the maximum line size</td></tr> |
| <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> |
| <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>SubstituteMaxLineLength 1m</code></td></tr> |
| <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr> |
| <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr> |
| <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> |
| <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_substitute</td></tr> |
| <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in httpd 2.4.11 and later</td></tr> |
| </table> |
| <p>The maximum line size handled by <code class="module"><a href="../mod/mod_substitute.html">mod_substitute</a></code> |
| is limited to restrict memory use. The limit can be configured |
| using <code class="directive">SubstituteMaxLineLength</code>. |
| The value can be given as the number of bytes and can be suffixed |
| with a single letter <code>b</code>, <code>B</code>, <code>k</code>, |
| <code>K</code>, <code>m</code>, <code>M</code>, <code>g</code>, |
| <code>G</code> to provide the size in bytes, kilobytes, megabytes |
| or gigabytes respectively.</p> |
| |
| <div class="example"><h3>Example</h3><pre class="prettyprint lang-config"><Location "/"> |
| AddOutputFilterByType SUBSTITUTE text/html |
| SubstituteMaxLineLength 10m |
| Substitute "s/foo/bar/ni" |
| </Location></pre> |
| </div> |
| |
| |
| </div> |
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