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List:       ast-users
Subject:    Re: [ast-users] Bug with arithmetic and variable substitution in long
From:       David Korn <dgk () research ! att ! com>
Date:       2011-12-08 0:13:05
Message-ID: 201112080013.pB80D5DI001576 () penguin ! research ! att ! com
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cc: ast-users@research.att.com
Subject: Re: [ast-users] Bug with arithmetic and variable substitution in long  here-docs
--------

> I'm writing to report a repeatable bug involving long here-documents
> that have both arithmetic and variable substitution.  This is the
> simplest script I can come up with that shows this problem:
> 
>    #!/bin/ksh
> 
>    FOO=1
>    BAR=foobarbaz
> 
>    cat <<#EOF
>        $(($FOO + 1))
>        $BAR meep
> 
>        # repeat the above two lines around 20,000 times
>    EOF
> 
> When this is run, ksh will substitute some of the $BAR's with blanks:
> 
>    tiferet:~ $> ksh foo.ksh | grep meep | grep -v foobarbaz
>     meep
>     meep
>     meep
>     meep
>     meep
> 
> Two things make it consistently work as expected.  The first is to
> remove all of the arithmetic substitution lines.  The second is to
> wrap BAR in braces:
> 
>    $(($FOO + 1))
>    ${BAR} meep
> 
> This is happening on both an older RedHat box with Version M 93s+
> 2008-01-31, and an up-to-date Debian testing box with Version JM 93u
> 2011-02-08.
> 
> Possibly relevant is this information:
> 
> http://lists.gnu.org/archive/html/bug-autoconf/2002-03/msg00069.html
> http://www.mail-archive.com/autoconf-patches@gnu.org/msg01276.html
> 
> However, this is much older, and their fix was to *omit* braces
> instead of add them.  In addition, my testing shows that there must be
> an arithmetic expression in the here-doc for this bug to manifest.
> 
> Thank you for your time.
> 
> --
> Troy
> 

Thanks for reporting this problem and for providing a way to reproduce
the problem.  I have found and fixed this problem for the next update.
If you are building from the source, I can send you a patch.

If you find any other problem with here-documents, (or any other problem),
please report them and they will be resolved.

David Korn
dgk@research.att.com
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