> On Jul 3, 2020, at 2:00 PM, Chris Elvidge <celvidge...@gmail.com> wrote:
>
> However 'N=0; echo $((!$N))' gives an error at the bash prompt.
> 'echo $[!$N]' echo's 1 as expected.
>
> My question - is $[...] actually obsolete?
It might tell you something that $[...] is not even mentioned in
the man page for bash 3.2.57, which is decidedly not the current
version.
> If so, what should I use at the bash prompt to get the same effect?
I expect that the error you encountered was caused by !$ expanding
to the last word of the previous command and making the contents
of $((...)) an invalid arithmetic expression. This didn't affect
your scripts because history expansion is not enabled in non-interactive
shells by default.
Try inserting a space.
$ N=0; printf %s\\n "$((! $N))"
1
You can even drop the $.
$ N=0; printf %s\\n "$((! N))"
1
vq
