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From: tps@chem.ucsd.edu (Tom Stockfisch)
Newsgroups: comp.unix.wizards
Subject: serious awk bug
Keywords: awk
Message-ID: <702@chem.ucsd.EDU>
Date: 14 Mar 90 06:02:46 GMT
Reply-To: tps@chem.ucsd.edu (Tom Stockfisch)
Organization: Chemistry Dept, UC San Diego
Lines: 49


The following awk script doesn't behave properly:

#! /bin/sh

awk '/^a*[^b]/	{  print "1:", $0 }
/^a*b/ 	{ print "2:", $0 }
'

When given the following input


b
ab


It produces the following output


2: b
1: ab
2: ab


Basically, the line "ab" should match only rule 2, but it matches both
rules.  The following script:


#! /bin/sh

awk '/^a*[^b]c/	{  print "1:", $0 }
/^a*bc/ 	{ print "2:", $0 }
'


works, producing the output

2: bc
2: abc


The corresponding lex program works fine.

I have run the awk script with both the new awk and old awk, on both
a system V machine (silicon graphics iris) and a 4BSD machine (celerity)
and all seem to fail.  
-- 

|| Tom Stockfisch, UCSD Chemistry	tps@chem.ucsd.edu