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Date: Fri, 29 Jun 2001 00:27:58 -0400
From: parv <parv_@yahoo.com>
To: Dave Tweten <tweten@nas.nasa.gov>
Cc: freebsd-questions@freebsd.org
Subject: Re: Bourne Shell Syntax Wierdness
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	freebsd-questions@freebsd.org
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In-Reply-To: <200106290144.f5T1itu01729@gilmore.nas.nasa.gov>; from tweten@nas.nasa.gov on Thu, Jun 28, 2001 at 06:44:54PM -0700
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so, Dave Tweten shared this in my lifetime...
> The sh man page says that the two operators "||" and "&&" have the same 
> precedence.  It also says that
> 
> 	a || b
> 
> means "execute b if a terminates abnormally" and
> 
> 	a && b
> 
> means "execute b if a terminates normally."
> 
> So I don't understand why
> 
> 	true || true && echo Oops!
> 
> prints "Oops!"
> 
> This is apparently not a bug in FreeBSD sh, because IRIX, IRIX64, and SunOS 
> Bourne/Korn shells work the same way, but it certainly runs counter to my 
> ability to read English and the contents of the man page.
> 
> Incidently,
> 
> 	true || { true && echo Oops! }
> 
> prints nothing -- which I would have expected with or without the "{}".
> 

sh & ksh man pages do say the quoted behaviour above. so does bash's.
however, bash's page adds this, under "Compund Commands" which is 
missing for sh & ksh:

  The  && and || operators do not execute expression2 if the
  value of expression1 is sufficient to determine the return
  value of the entire conditional expression.

notice the word "sufficient"; so due to lack of proper grouping, to 
mitigate ambiguity, all three evaluates the expression as...

# ( true || true ) && echo Oops!

...i may be stating the obvious; mind you that i am only hypothisizing
here, nothing more than that, lest somebody is bent on getting the above
desired evaluation...

-- 
 so, do you like word games or scrabble?
	 - parv

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