[9fans] Why Plan 9 uses $ifs instead of $IFS?

[giacomo@tesio.it (Giacomo Tesio)]

>
> In *rc* you use quotation marks when you want a syntax character to
> appear in an argument, or an argument that is the empty string, and at no
> other time. IFS is no longer used, *except in the one case where it was
> indispensable*: converting command output into argument lists during
> command substitution.


So, I undestood: it used to use IFS in that one case.

I got it now: the fact that IFS was named ifs was not a relevant for the
discourse, and thus omitted.

Still I'm a bit surprised that such change in the conventions provides no
practical advantage: the taste changes with age, but costs accumulate... :-)


BTW, thanks for your answers!


Giacomo


2017-10-17 17:18 GMT+02:00 Charles Forsyth <charles.forsyth at gmail.com>:

> since for example the original Rc paper still referred to $IFS.
>
>
> really? the only references to IFS I can find are in comparisons of $ifs
> to the Bourne shell's $IFS
>
> On 17 October 2017 at 16:05, Giacomo Tesio <giacomo at tesio.it> wrote:
>
>> Really? Just aesthetics? :-o
>> I supposed it had some practical goal I was missing, since for example
>> the original Rc paper still referred to $IFS.
>>
>> This would flips the question a bit: I wonder why the same designers
>> chose uppercase variable names while designing Unix... :-)
>>
>>
>> Giacomo
>>
>> 2017-10-17 16:39 GMT+02:00 Dan Cross <crossd at gmail.com>:
>>
>>> On Tue, Oct 17, 2017 at 10:38 AM, Giacomo Tesio <giacomo at tesio.it>
>>> wrote:
>>> > Out of curiosity, do anybody know why Plan9 designers chose lowercase
>>> > variables over uppercase ones?
>>> >
>>> > At first, given the different conventions between rc and sh (eg $path
>>> is an
>>> > array, while $PATH is a string), I supposed Plan 9 designers wanted to
>>> > prevent conflict with unix tools relying to the older conventions.
>>> >
>>> > However, I'm not sure this was the main reason, as this also open to
>>> subtle
>>> > issues: if a unix shell modifies $IFS and then invoke an rc script,
>>> such
>>> > script will ignore the change and keep using the previous $ifs.
>>> >
>>> >
>>> > As far as I can see, APE does not attempt any translation between the
>>> two
>>> > conventions, so maybe I'm just missing something obvious...
>>> >
>>> >
>>> > Do anyone know what considerations led to such design decision?
>>>
>>> Aesthetics.
>>>
>>>
>>
>
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