On Wed, Apr 24, 2019 at 09:58:42AM -0400, Chet Ramey wrote:
> The SVR4.2 Bourne shell, as another data point, behaves like bash. Since
> it doesn't have arithmetic expansion, you have to use something it does
> handle internally, like ${n:=2}. I don't know what ksh88, the other POSIX
> historical reference implementation, does.
# uname -a
HP-UX vandev B.10.20 A 9000/778 2000153729 two-user license
# exec ksh
# set -o vi
# n=0; : $((n=n+1)); echo "$n"
1
# n=0; /bin/true > $((n=n+1)); echo "$n"
0
Looks like it changed between ksh88 and ksh93.
