envfilesubst

envfilesubst is a variation of gettext's envsubst, with a different modus operandi.

Firstly, instead of reading the current environment it reads from file in traditional "envfile" format.

Secondly, it will read input from stdin replacing all variable references that can be matched with the envfile. If variables are not explicitly mentioned in the envfile, the references will be left untouched (instead of replacing them with an empty string).

Git

The main git repo is: https://git.netflux.io/rob/envfilesubst

It is also mirrored on GitHub: https://github.com/rfwatson/envfilesubst

Installation

go install git.netflux.io/rob/envfilesubst@latest

Usage

Given an envfile:

# myenvfile
FOO=bar
X=1

Then:

echo "FOO is $FOO and X is ${X}. I don't know $BAZ." | envfilesubst -f myenvfile

The output is:

FOO is bar and X is 1. I don't know $BAZ.