On 03/07/2020 10:39 pm, Lawrence Velázquez wrote:
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
Thanks for the info.
It also explains why I couldn't find a reference to $[...] except in the
reference I quoted.
--
Chris Elvidge
5 Ebor Park, Appleton Roebuck, York. YO23 7DZ.
Tel (Mob): +447443472958 mailto:celvi...@outlook.com
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