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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

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