From: Rich Bowen <rbowen@apache.org>
Date: Thu, 21 May 2026 16:24:04 +0000 (+0000)
Subject: Clarify the role of ! in regular expressions and backreferences
X-Git-Tag: 2.4.68-rc1-candidate~102
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=af404cfa1a8744b79a9eeda4c590ee7aa3201b80;p=thirdparty%2Fapache%2Fhttpd.git

Clarify the role of ! in regular expressions and backreferences

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1934481 13f79535-47bb-0310-9956-ffa450edef68
---

diff --git a/docs/manual/mod/mod_rewrite.xml b/docs/manual/mod/mod_rewrite.xml
index 56ff647891..ac83448f6f 100644
--- a/docs/manual/mod/mod_rewrite.xml
+++ b/docs/manual/mod/mod_rewrite.xml
@@ -443,7 +443,7 @@ RewriteRule "^/ex/(.*)" "${examplemap:$1}"
 <description>Defines a condition under which rewriting will take place
 </description>
 <syntax> RewriteCond
-      <em>TestString</em> <em>CondPattern</em> [<em>flags</em>]</syntax>
+      <em>TestString</em> [!]<em>CondPattern</em> [<em>flags</em>]</syntax>
 <contextlist><context>server config</context><context>virtual host</context>
 <context>directory</context><context>.htaccess</context></contextlist>
 <override>FileInfo</override>
@@ -456,6 +456,10 @@ RewriteRule "^/ex/(.*)" "${examplemap:$1}"
       the current state of the URI matches its pattern, <strong
       >and</strong> if these conditions are met.</p>
 
+      <p>If the <em>CondPattern</em> is prefixed with a <code>!</code> the
+      condition is determined to be true only if the the
+      <em>CondPattern</em> does not match.</p>
+
       <p><em>TestString</em> is a string which can contain the
       following expanded constructs in addition to plain text:</p>
 
@@ -468,6 +472,10 @@ RewriteRule "^/ex/(.*)" "${examplemap:$1}"
           <code>RewriteRule</code> which is subject to the current
           set of <code>RewriteCond</code> conditions. $0 provides
           access to the whole string matched by that pattern.
+
+          <note>Backreferences are only defined if the pattern 
+          matches. Thus, if the pattern is prefixed with 
+          <code>!<.code>, no backreferences are ever defined.</note>
         </li>
         <li>
           <strong>RewriteCond backreferences</strong>: These are
@@ -477,6 +485,10 @@ RewriteRule "^/ex/(.*)" "${examplemap:$1}"
           <code>RewriteCond</code> in the current set
           of conditions. %0 provides access to the whole string matched by
           that pattern.
+
+          <note>Backreferences are only defined if the pattern 
+          matches. Thus, if the pattern is prefixed with 
+          <code>!<.code>, no backreferences are ever defined.</note>
         </li>
         <li>
           <strong>RewriteMap expansions</strong>: These are
@@ -1072,7 +1084,7 @@ RewriteRule  "^/$"                 "/homepage.std.html"     [L]
 <name>RewriteRule</name>
 <description>Defines rules for the rewriting engine</description>
 <syntax>RewriteRule
-      <em>Pattern</em> <em>Substitution</em> [<em>flags</em>]</syntax>
+      [!]<em>Pattern</em> <em>Substitution</em> [<em>flags</em>]</syntax>
 <contextlist><context>server config</context><context>virtual host</context>
 <context>directory</context><context>.htaccess</context></contextlist>
 <override>FileInfo</override>
@@ -1089,6 +1101,10 @@ RewriteRule  "^/$"                 "/homepage.std.html"     [L]
       expression</glossary></a>.  What this pattern is compared against varies depending
       on where the <directive>RewriteRule</directive> directive is defined. </p>
 
+      <p>If the pattern is prefixed with a <code>!</code> the
+      substitution will be performed only if the the
+      <em>pattern</em> does not match.</p>
+
 <note><title><a id="what_is_matched" name="what_is_matched">What is matched?</a></title>
 
 <ul>