Compare Configuration Files

#!/bin/bash

EXAMPLE_FILE=local.env.example
LOCAL_FILE=local.env

if [[ ! -f "$LOCAL_FILE" ]]; then
    echo "local environment file doesn't exist"
    exit 0
fi

if [[ ! -f "$EXAMPLE_FILE" ]]; then
    echo "example environment file doesn't exist"
    exit 1
fi

LOCAL_CONTENTS=$(cat ./${LOCAL_FILE} | grep export | sed 's/^export //g' | awk -F'=' '{print $1}')
EXAMPLE_CONTENTS=$(cat ./${EXAMPLE_FILE} | grep export | sed 's/^export //g' | awk -F'=' '{print $1}')

ERRS=()

# Process contents of EXAMPLE_CONTENTS, line-by-line.
# IFS is empty as we don't want to separate the contents on each line
while IFS='' read -ra ADDR; do
  for i in "${ADDR[@]}"; do
    # If the env var is commented out, ignore it
    if [ "${i:0:1}" == "#" ]; then
      continue
    fi

    EXISTS_IN_EXAMPLE=$(echo "$EXAMPLE_CONTENTS" | grep "$i")

    # If the string is null (empty)
    if [ -z "$EXISTS_IN_EXAMPLE" ]; then
      ERRS+=("$i")
    fi
  done
done <<< "$LOCAL_CONTENTS"

if [[ ! ${#ERRS[@]} -eq 0 ]]; then
    echo "The following environment variables are defined in $LOCAL_FILE, but not in $EXAMPLE_FILE:"
    echo "${ERRS[@]}"
    exit 1
fi