Simple calculator - from https://github.com/mathiasbynens/dotfiles/blob/master/.functions

calc

# Simple calculator - from https://github.com/mathiasbynens/dotfiles/blob/master/.functions
function calc() {
	local result=""
	result="$(printf "scale=10;$*\n" | bc --mathlib | tr -d '\\\n')"
	#                       └─ default (when `--mathlib` is used) is 20
	#
	if [[ "$result" == *.* ]]; then
		# improve the output for decimal numbers
		printf "$result" |
		sed -e 's/^\./0./'        `# add "0" for cases like ".5"` \
		    -e 's/^-\./-0./'      `# add "0" for cases like "-.5"`\
		    -e 's/0*$//;s/\.$//'   # remove trailing zeros
	else
		printf "$result"
	fi
	printf "\n"
}