unset variables, was Re: please correct my ugly hack

[Dan Manthey]

On Thu, 2 Jun 2005, Stepan Kasal wrote:

> it uses    test "x$VAR" = x
>
> Thus the manual should use the term "is nonempty", not "is set".
>
> (One of the reasons for this behaviour is that unset is not portable.)

It's documented that the builtin `unset' is non-portable, but what about
the use of unset variables vs. empty variables?  Is this distinction
always meaningful?  (Some of the caveats about MS DOS suggest not?)  Also,
I know that ${var:-default} is not portable.  Is ${var-default}?  For that
matter, I know you can set bash to error out on $var for an unset var,
which would require ${var-}.  I'm ignorant:  is this behavior turned off
by AC_INIT (or whatever)?

-Dan

autoconf-20041027-check_prog.patch
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