percentage.sh: quick and dirty command line percentage calculator

percentage.sh

#!/usr/bin/env bash

# Copyright 2017 Ryan McKern <ryan@orangefort.com>

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#     http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

percentage(){
  [[ ${#} -ne 2 ]] && return 1

  # Using printf and bc like this minimizes the number of subshells
  # that are opened, allows bc to round the answer to something
  # human-readable, and lets printf truncate it out to 4 significant digits
  printf "%0.2f\\n" "$(bc <<< "scale=4; (${1} / ${2}) * 100")"
}

usage(){
  cat <<-USAGE
		$(basename "${0}"): quickly determine what percent <a> is of <b>, rounded to two decimals of precision

		usage:
		  \$ $(basename "${0}") 42 84
		  50.00
	USAGE
}

if [[ ${#} -ne 2 ]]; then
  usage 1>&2
  exit 1
fi

percentage "${1}" "${2}"