Command substitution now works inside arithmetic expressions in *bash* Previously, *bash* did not save input line state across recursive calls to the shell parser, causing the shell to fail to parse command substitution inside arithmetic expressions. For example, the following command failed: for point in "/boot"; do disk_dir["$( df -P $point | awk '{print $1}' )"]=1; done This bug has been fixed, *bash* now saves input line state before making recursive calls to the parser, and command substitution now works inside arithmetic expressions.