複数の変数名の変数値存在チェックを行うBashスクリプト断片

check_required_vars.sh

#!/bin/bash

# required variables
required_vars=("FOO" "BAR" "BAZ")

# check defined
for VAR_NAME in "${required_vars[@]}"; do
  eval var_temp='$'$VAR_NAME
  if [[ -z "$var_temp" ]]; then
    echo "$VAR_NAME is undefined." 1>&2
    usage_exit
  fi
  unset var_temp
done
unset required_vars