Bash - Parse environment variables in bash function

Question

I have a bash function that retrieves environment variables from a .env file.

In my .env file I have the following variables

USER=luis
IMAGE_NAME=application
IMAGE_VERSION=latest
IMAGE_TAG=${USER}/${IMAGE_NAME}:${IMAGE_VERSION}

In my bash script I have my env function

function dotenv::get() {
  variable=$(grep ^"${1}"= "$(pwd)/.env" | xargs)
  IFS="=" read -ra variable <<< "${variable}"

  echo "${variable[1]}"
}

When I execute dotenv::get IMAGE_TAG.

Expected result: luis/application:latest

Current result: ${USER}/${IMAGE_NAME}:${IMAGE_VERSION}

I'm aware my function is incomplete, however I'm not sure what are the next steps to achieve my objective.

question from:https://stackoverflow.com/questions/65892044/bash-parse-environment-variables-in-bash-function

Answer 1

The file looks like it wants to keep shell-ish syntax. If so, just source it:

. ./.env
echo "$IMAGE_TAG"

dotenv::get() { 
    . ./.env;
    echo "${!1}"
}

If this is not your intention, then implement a whole parser of variables from a file with a ${...} variable substitution of already set variables.