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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
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#
#
#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.
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