Lambros Petrou
"We are what we repeatedly do. Excellence then, is not an act, but a habit!" — Aristotle

Export environment variables from multiple files using Bash on Linux

Problem

Recently, I have updated the deployment scripts of my website and for some tasks I wanted to have certain environment variables available in my scripts. For example, I wanted to invalidate the Cloudfront distribution so that I don’t have to wait for the cache to expire before serving the new content, and I needed the --distribution-id.

I looked for the easiest way to export environment variables from key-value pairs in a file, and I was delighted to see that it can done with a single line!

Solution

The solution is based on this StackOverflow answer.

Assuming the following aws.environment file:

DISTRIBUTION_ID=xxxxxxxxx
S3_BUCKET=www.example.com

The following script will export the above key-value pairs as environment variables.

#!/usr/bin/env bash

source <(sed -E -n 's/[^#]+/export &/ p' aws.environment)

# ... Commands that use the above variables i.e. echo "$DISTRIBUTION_ID"

In addition, I didn’t want to limit myself only to one file of environment variables because I would like to version control some of them in git. So, I wanted to scan and export variables from all the files in a given directory. This can be done using the following script.

#!/usr/bin/env bash

source <(find ./build-tool/env/ -type f -exec sed -E -n 's/[^#]+/export &/ p' {} +)

# ... Commands that use the above variables

This final adaptation uses the find command to read all files in the ./build-tool/env directory and for each one exports its key-value pairs as environment variables.

That’s it! Once again, knowledge of some nifty Linux commands saves the day.