Replace all {{VAR_NAME}} tokens with their corresponding environment variable values into an `env.json` file

amend_static_env.sh

#!/usr/bin/env bash

APP_ROOT="${0%/*}/.."
APP_DIST="$APP_ROOT/build"

mkdir -p "$APP_DIST"

cp "$APP_ROOT/src/env.json.tpl" "$APP_DIST/env.json"

# replace all {{VAR_NAME}} tokens with their corresponding environment variable value
for key in `egrep -io '{{[A-Z_0-9]+}}' src/env.json.tpl | egrep -io '[A-Z_0-9]+'`; do
  sed -i '' -e "s|{{${key}}}|${!key}|g" "$APP_DIST/env.json"
done