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

[giacomo@tesio.it (Giacomo Tesio)]

Also, why NPROC has been left uppercase? :-)


Giacomo

2017-10-17 17:45 GMT+02:00 Giacomo Tesio <giacomo at tesio.it>:

> 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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