Re: How does quote removal work with alternative forms of parameter expansion?

[Chet Ramey]

On 5/26/24 8:38 PM, Philippe Cerfon wrote:

> > An interesting behavior is that
> > the «"» inside the double quotations toggles the expansion behavior
> > (as if the first " inside double quotes is paired with the opening
> > double quotation, and the second " inside double quotes is paired with
> > the closing double quotation):

This is the historical Bourne shell behavior, which ksh93 preserves for
historical compatibility.

> Why does:
> $ bar='1 2'
> $ printf '%s\n' "${unset_var:-"$bar"}"
>
> then result in:
> 1 2
> and not:
> 1
> 2

Because all the modern shell authors thought that aspect of the old Bourne
shell behavior was not worth preserving. Everyone agrees the double quotes
surrounding the expansion should inhibit word splitting. We just disagree
on some aspects of what to do about double quotes appearing on the rhs of
the operator.

You have to do something: either the double quotes on the rhs are special,
in which case they have meaning, affect processing of the characters they
enclose, and are removed, or they aren't, in which case they don't affect
processing but are somehow removed anyway.

In the early days we were a little more concerned about original Bourne
shell compatibility, because we wanted bash to run on 4.3 BSD, which
still used the 7th edition sh. So the historical bash behavior is kind of
a compromise.

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/

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