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Changes to manual/html_node/Back_002dreferences-and-Subexpressions.html
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From: |
Karl Berry |
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Subject: |
Changes to manual/html_node/Back_002dreferences-and-Subexpressions.html |
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Date: |
Sun, 24 May 2009 18:43:05 +0000 |
CVSROOT: /web/grep
Module name: grep
Changes by: Karl Berry <karl> 09/05/24 18:43:01
Index: manual/html_node/Back_002dreferences-and-Subexpressions.html
===================================================================
RCS file: manual/html_node/Back_002dreferences-and-Subexpressions.html
diff -N manual/html_node/Back_002dreferences-and-Subexpressions.html
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ manual/html_node/Back_002dreferences-and-Subexpressions.html 24 May
2009 18:42:58 -0000 1.1
@@ -0,0 +1,65 @@
+<html lang="en">
+<head>
+<title>Back-references and Subexpressions - GNU Grep 2.5.4</title>
+<meta http-equiv="Content-Type" content="text/html">
+<meta name="description" content="GNU Grep 2.5.4">
+<meta name="generator" content="makeinfo 4.13">
+<link title="Top" rel="start" href="index.html#Top">
+<link rel="up" href="Regular-Expressions.html#Regular-Expressions"
title="Regular Expressions">
+<link rel="prev" href="Anchoring.html#Anchoring" title="Anchoring">
+<link rel="next" href="Basic-vs-Extended.html#Basic-vs-Extended" title="Basic
vs Extended">
+<link href="http://www.gnu.org/software/texinfo/"; rel="generator-home"
title="Texinfo Homepage">
+<!--
+This manual is for `grep', a pattern matching engine.
+
+Copyright (C) 1999, 2000, 2001, 2002, 2005, 2008, 2009 Free
+Software Foundation, Inc.
+
+ Permission is granted to copy, distribute and/or modify this
+ document under the terms of the GNU Free Documentation License,
+ Version 1.3 or any later version published by the Free Software
+ Foundation; with no Invariant Sections, with no Front-Cover Texts,
+ and with no Back-Cover Texts. A copy of the license is included
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+</head>
+<body>
+<div class="node">
+<a name="Back-references-and-Subexpressions"></a>
+<a name="Back_002dreferences-and-Subexpressions"></a>
+<p>
+Next: <a rel="next" accesskey="n"
href="Basic-vs-Extended.html#Basic-vs-Extended">Basic vs Extended</a>,
+Previous: <a rel="previous" accesskey="p"
href="Anchoring.html#Anchoring">Anchoring</a>,
+Up: <a rel="up" accesskey="u"
href="Regular-Expressions.html#Regular-Expressions">Regular Expressions</a>
+<hr>
+</div>
+
+<h3 class="section">3.5 Back-references and Subexpressions</h3>
+
+<p><a name="index-subexpression-237"></a><a
name="index-back_002dreference-238"></a>
+The back-reference ‘<samp><span
class="samp">\</span><var>n</var></samp>’, where <var>n</var> is a single
digit, matches
+the substring previously matched by the <var>n</var>th parenthesized
subexpression
+of the regular expression.
+For example, ‘<samp><span class="samp">(a)\1</span></samp>’
matches ‘<samp><span class="samp">aa</span></samp>’.
+When used with alternation, if the group does not participate in the match then
+the back-reference makes the whole match fail.
+For example, ‘<samp><span class="samp">a(.)|b\1</span></samp>’
+will not match ‘<samp><span class="samp">ba</span></samp>’.
+When multiple regular expressions are given with
+‘<samp><span class="samp">-e</span></samp>’ or from a file
(‘<samp><span class="samp">-f file</span></samp>’),
+back-references are local to each expression.
+
+ </body></html>
+
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