Re: nmh 1.8RC2, xlbiff, and $HOME

[Ken Hornstein]

>Ken, you, and David all seem irked by unset and set-but-empty being
>treated differently, as if you'd like a binary outcome by first
>conflating the ternary input to binary.

Sigh.  I'll try to make my point clearer, but I recognize we're not going
to agree on this.  Since David is driving this release, I defer to his
decision in terms of changing the behavior for the next release candidate
(I would vote for making the behavior of unset and empty be the same, but
I consider David the God Emperor of nmh 1.8, so it's up to him).

You ask the question:

What is the user trying to achieve by explicitly setting an empty HOME? 

To me, the answer is obvious: they were trying to create a clean
environment.  You say that they could do that by unsetting HOME; well,
count me in the pool of people who did not know until now that 'unset'
even existed.  I mean, I vaguely knew that there was a difference
between a variable that was never used and one that was set to an empty
string, but as far as I could tell there wasn't a PRACTICAL difference
between those two states and I certainly wouldn't expect an application
to treat those states differently.  I suspect the person who wrote that
test for xlbiff didn't know about 'unset' either and would be bewildered
that there is any difference in behavior.  Also, some quick testing suggests
that:

% HOME='' command

Does the expected thing but:

% unset HOME command

Simply unsets the HOME and 'command' variables.  I realize you could do
that in a subshell but it just seems awkward, and the idiom of doing

% FOO=value command

to change an environment variable is very common and I see why people
would just use that.

I have read your arguments carefully and ... well, I still do not agree
that there should be a difference in behavior between an unset HOME and
an empty HOME.  To me there is no ambiguity and they are the same, even
if it's a technically different variable state.  Again, I realize we're
just not going to agree on this.

--Ken