Double Parentheses
Double-Parentheses permits arithmetic expansion and evaluation. it allowing C-style manipulation of variables; for example, ((var++))
$ a=$((8+8))
$ echo $a #16
$ ((a++))
$ echo $a #17
# we can also use let
$ let a++
$ echo $a #18
Double-Parentheses permits arithmetic expansion and evaluation. it allowing C-style manipulation of variables; for example, ((var++))
$ a=$((8+8))
$ echo $a #16
$ ((a++))
$ echo $a #17
# we can also use let
$ let a++
$ echo $a #18