Re: [PATCH 2/2] config.status: minimize use of $tmp

[Ralf Wildenhues]

Hi Eric,

* Eric Blake wrote on Mon, Aug 30, 2010 at 06:41:47PM CEST:
> On 08/27/2010 01:24 PM, Eric Blake wrote:
> >-  tmp=
> >+  tmp= ac_tmp=
> >    trap 'exit_status=$?
> >-  { test -z "$tmp" || test ! -d "$tmp" || rm -fr "$tmp"; }&&  exit 
> >$exit_status
> >+  { test ! -d "${ac_tmp:=$tmp}" || rm -fr "$ac_tmp"; }&&  exit $exit_status
> 
> And then I promptly used it incorrectly.  Per what we just
> documented, we cannot assume that ${a=b} takes effect in the parent
> shell if we are executing a child command like test

I don't follow this.  Surely that Posix reference hints at
http://austingroupbugs.net/view.php?id=255
and is meant for assignments *before* commands only, as in for example
  ac_tmp=$tmp test ! -d "$ac_tmp"

but not the code above.

Can you help me understand?

Thanks,
Ralf