Loading dotenv files with exports and interpolations without override the current vars

load_dotenv.sh

#!/usr/bin/env bash

# This function loads variables from a .env (dotenv format) files without
# override the current variables. It will fix the relative paths.
# 
# Example:
# 
#   $ export ENV=developer
#   $ cat dotenvs/.env
#   ENV=staging
#   ENV_UP="${ENV^^}"
#   export ENV_NAME=${ENV}
#   ENV_PATH="../"
#   
#   $ loadDotenvFile ./.env true
#   $ env | grep ENV
#   ENV=staging
#   ENV_NAME=staging
#   ENV_UP="STAGING"
#   ENV_PATH="./"
#
loadDotenvFile() {
  if [ -d "${1}" ]; then
    log "Path ${1} exist, but is a directory"
  elif [ -f "${1}" ]; then
    envfile="${1}"
    # https://regexr.com/4dnme
    # https://stackoverflow.com/a/2821201/469463
    log "Load envs from ${envfile}"
    content="$(sed -E 's/^(export[[:space:]]*)?([a-zA-Z_]{1,}[a-zA-Z0-9_]{0,})={1}(.*)$/export \2=\${\2:-\3}/g' "${envfile}")"
    eval "${content}"

    fixpath="${2:-false}"
    if [[ "$fixpath" == "true" ]]; then
      # Fix relative values
      folder="$(dirname "${envfile}")"
      parent="$(dirname "${folder}")"
      vars=()
      while IFS='' read -r line; do vars+=("$line"); done < <(printenv | grep '=\.\.\?\/')
      for var in "${vars[@]}"; do
        eval "export $(echo "$var" | sed -E 's|^(.*=)\.(\/.*)|\1'"${folder}"'\2|g')"
        eval "export $(echo "$var" | sed -E 's|^(.*=)\.\.(\/.*)|\1'"${parent}"'\2|g')"
      done
    fi
  fi
}