It appears that
$[expr] performs arithmetic expansion just like
$((expr)). But I can't find any mention of
$[ in the bash manual. This command gives no results:
gunzip -c /usr/share/man/man1/bash.1.gz | grep -E '\$\['
What is this operator and is its behavior standardized anywhere?
My bash version: GNU bash, version 3.2.51(1)-release (x86_64-apple-darwin13)