Re: feature todo .. be able to unset vars at assignment stage , without unset util , for coding language fair extendment

[Greg Wooledge]

On Fri, Feb 23, 2024 at 07:23:49AM -0500, Zachary Santer wrote:
> On Thu, Feb 22, 2024 at 10:58 PM Greg Wooledge <greg@wooledge.org> wrote:
> 
> > On Thu, Feb 22, 2024 at 10:52:59PM -0500, Zachary Santer wrote:
> > >
> > > Maybe something like var=${<>} could unset var. Something between the
> > curly
> > > braces that would just be a syntax error otherwise.
> >
> > ${} is nicely erroneous, currently, as is ${~}.
> >
> 
> This would look inconsistent with how the rest of variable assignments work
> when you're trying to unset an entire array, though.
> 
> var='whatever' sets var[0] if var is already an indexed or
> associative array, so expecting var=${<>} or var=${~} to unset the entire
> array doesn't work.

Assignments preceding a simple command create environment variables
for the duration of the simple command.  Array variables cannot be
exported into the environment, so they're already disqualified from
consideration here.

With all that said, I don't plan to implement this, nor would I expect
Chet to do so if it's a pain.  I could see a *small* benefit to having
this syntactic feature available, but not enough to demand it.  Existing
scripts that use commands like

    (unset DISPLAY; xsomething)

will continue to work, and provide the same results that the proposed
feature would provide.  Such commands are pretty rare in my experience.