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grep branch, master, updated. v3.3-59-gab73e1c

From: Paul Eggert
Subject: grep branch, master, updated. v3.3-59-gab73e1c
Date: Mon, 30 Dec 2019 13:49:18 -0500 (EST)

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      from  fdee61d847ed6c78901bd5620f1d421c51468181 (commit)

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commit ab73e1c64222872c58879c3684d2fd206f76154d
Author: Paul Eggert <address@hidden>
Date:   Mon Dec 30 10:41:43 2019 -0800

    doc: don’t encourage back-references
    * doc/grep.texi (Usage): Remove palindrome question.  Bondioni’s
    RE makes grep issue a ‘grep: stack overflow’ diagnostic, and we
    shouldn’t be encouraging fancy back-references anyway, due to all
    the bugs in this area (Bug#26864).  Plus, the allusion to
    “GNU extensions” doesn't seem to be correct here.

diff --git a/doc/grep.texi b/doc/grep.texi
index aceaf33..7c2b865 100644
--- a/doc/grep.texi
+++ b/doc/grep.texi
@@ -1801,31 +1801,6 @@ cat /etc/passwd | grep 'alain' - /etc/motd
 @end example
-@cindex palindromes
-How to express palindromes in a regular expression?
-It can be done by using back-references;
-for example,
-a palindrome of 4 characters can be written with a BRE:
-grep -w -e '\(.\)\(.\).\2\1' file
-@end example
-It matches the word ``radar'' or ``civic.''
-Guglielmo Bondioni proposed a single RE
-that finds all palindromes up to 19 characters long
-using @w{9 subexpressions} and @w{9 back-references}:
-grep -E -e '^(.?)(.?)(.?)(.?)(.?)(.?)(.?)(.?)(.?).?\9\8\7\6\5\4\3\2\1$' file
-@end smallexample
-Note this is done by using GNU ERE extensions;
-it might not be portable to other implementations of @command{grep}.
 Why is this back-reference failing?


Summary of changes:
 doc/grep.texi | 25 -------------------------
 1 file changed, 25 deletions(-)


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