dotenv-filler

A simple environment-to-file script. Match-and-replace values of key-value pairs in a file directly from your environment. Can be used for example in CI pipelines to generate .env files from their example equivalents.

What it does

The script goes through every key in a given key-value file. If a key has a value in the environment, the script replaces its value with the one from the environment. You can also provide a prefix to help keeping your variables separate.

Requirements

• POSIX compatible shell
• sed utility
• env utility
• tr utility

Usage

sh dotenv-filler.sh FILE [VAR_PREFIX]

Parameters:

• FILE The key-value file to apply changes to
• VAR_PREFIX - Look for the variables with this prefix in the environment. This value is sanitized: All &*+,./:;@|~- characters are replaced with underscores (_) and then all non-alphanumeric characters (except _) are dropped. Finally, the value is changed to all uppercase for a usual env varaible format. This helps when one wants to use strings from other sources (for example git branch names) as prefix.

Examples

Let's take a file named .env with the following content:

FIRST_VARIABLE=
SECOND_VARIABLE=255

Without using a prefix:

Running FIRST_VARIABLE=test sh dotenv-filler.sh .env will change the contents of the file to the following:

FIRST_VARIABLE=test
SECOND_VARIABLE=255

Using a prefix:

Running PRE_SECOND_VARIABLE=hello sh dotenv-filler.sh .env PRE will change the contents of the file to the following:

FIRST_VARIABLE=
SECOND_VARIABLE=hello