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# Subject: fixme
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# From: laura@madonnaweb.com (laura fairhead)
# Newsgroups: comp.lang.awk
# Subject: bug in gawk3.1.0 regex code
# Date: Wed, 08 May 2002 23:31:40 GMT
# Organization: that'll be the daewooo :)
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# Xref: dfw-artgen comp.lang.awk:13059
#
#
# I believe I've just found a bug in gawk3.1.0 implementation of
# extended regular expressions. It seems to be down to the alternation
# operator; when using an end anchor '$' as a subexpression in an
# alternation and the entire matched RE is a nul-string it fails
# to match the end of string, for example;
#
# gsub(/$|2/,"x")
# print
#
# input = 12345
# expected output = 1x345x
# actual output = 1x345
#
# The start anchor '^' always works as expected;
#
# gsub(/^|2/,"x")
# print
#
# input = 12345
# expected output = x1x345
# actual output = x1x345
#
# This was with POSIX compliance enabled althought that doesn't
# effect the result.
#
# I checked on gawk3.0.6 and got exactly the same results however
# gawk2.15.6 gives the expected results.
#
# I'm about to post a bug report about this into gnu.utils.bug
# but I thought I'd post it here first in case anyone has
# any input/comments/whatever ....
#
# Complete test results were as follows;
#
# input 12345
# output gsub(/regex/,"x",input)
#
# regex output
# (^) x12345
# ($) 12345x
# (^)|($) x12345x
# ($)|(^) x12345x
# (2) 1x345
# (^)|2 x1x345
# 2|(^) x1x345
# ($)|2 1x345
# 2|($) 1x345
# (2)|(^) x1x345
# (^)|(2) x1x345
# (2)|($) 1x345
# ($)|(2) 1x345
# .((2)|(^)) x345
# .((^)|(2)) x345
# .((2)|($)) x34x
# .(($)|(2)) x34x
# x{0}((2)|(^)) x1x345
# x{0}((^)|(2)) x1x345
# x{0}((2)|($)) 1x345
# x{0}(($)|(2)) 1x345
# x*((2)|(^)) x1x345
# x*((^)|(2)) x1x345
# x*((2)|($)) 1x345
# x*(($)|(2)) 1x345
#
# Here's the test program I used, a few of the cases use ERE {n[,[m]]}
# operators so that will have to be commented out or have a check
# added or something (should have put a conditional in I know... ;-)
#
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#
BEGIN{
TESTSTR="12345"
print "input "TESTSTR
print "output gsub(/regex/,\"x\",input)"
print ""
print "regex output"
$0=TESTSTR
gsub(/(^)/,"x")
print "(^) "$0
$0=TESTSTR
gsub(/($)/,"x")
print "($) "$0
$0=TESTSTR
gsub(/(^)|($)/,"x")
print "(^)|($) "$0
$0=TESTSTR
gsub(/($)|(^)/,"x")
print "($)|(^) "$0
$0=TESTSTR
gsub(/2/,"x")
print "(2) "$0
$0=TESTSTR
gsub(/(^)|2/,"x")
print "(^)|2 "$0
$0=TESTSTR
gsub(/2|(^)/,"x")
print "2|(^) "$0
$0=TESTSTR
gsub(/($)|2/,"x")
print "($)|2 "$0
$0=TESTSTR
gsub(/2|($)/,"x")
print "2|($) "$0
$0=TESTSTR
gsub(/(2)|(^)/,"x")
print "(2)|(^) "$0
$0=TESTSTR
gsub(/(^)|(2)/,"x")
print "(^)|(2) "$0
$0=TESTSTR
gsub(/(2)|($)/,"x")
print "(2)|($) "$0
$0=TESTSTR
gsub(/($)|(2)/,"x")
print "($)|(2) "$0
$0=TESTSTR
gsub(/.((2)|(^))/,"x")
print ".((2)|(^)) "$0
$0=TESTSTR
gsub(/.((^)|(2))/,"x")
print ".((^)|(2)) "$0
$0=TESTSTR
gsub(/.((2)|($))/,"x")
print ".((2)|($)) "$0
$0=TESTSTR
gsub(/.(($)|(2))/,"x")
print ".(($)|(2)) "$0
$0=TESTSTR
gsub(/x{0}((2)|(^))/,"x")
print "x{0}((2)|(^)) "$0
$0=TESTSTR
gsub(/x{0}((^)|(2))/,"x")
print "x{0}((^)|(2)) "$0
$0=TESTSTR
gsub(/x{0}((2)|($))/,"x")
print "x{0}((2)|($)) "$0
$0=TESTSTR
gsub(/x{0}(($)|(2))/,"x")
print "x{0}(($)|(2)) "$0
$0=TESTSTR
gsub(/x*((2)|(^))/,"x")
print "x*((2)|(^)) "$0
$0=TESTSTR
gsub(/x*((^)|(2))/,"x")
print "x*((^)|(2)) "$0
$0=TESTSTR
gsub(/x*((2)|($))/,"x")
print "x*((2)|($)) "$0
$0=TESTSTR
gsub(/x*(($)|(2))/,"x")
print "x*(($)|(2)) "$0
$0=TESTSTR
gsub(/x{0}^/,"x")
print "x{0}^ "$0
$0=TESTSTR
gsub(/x{0}$/,"x")
print "x{0}$ "$0
$0=TESTSTR
gsub(/(x{0}^)|2/,"x")
print "(x{0}^)|2 "$0
$0=TESTSTR
gsub(/(x{0}$)|2/,"x")
print "(x{0}$)|2 "$0
}
#
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#
# byefrom
#
# --
# laura fairhead # laura@madonnaweb.com http://lf.8k.com
# # if you are bored crack my sig.
# 1F8B0808CABB793C0000666667002D8E410E83300C04EF91F2877D00CA138A7A
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# 80F2978A1A6E5D6F5133B67B6113178DC1059526698AFE5C17A5187E7D930492
#