go get github.com/MarioCarrion/templenv
templenv is a command line program for generating output from environment variables by using Go templates, a key piece in the Docker Full Development Workflow. os.StdOut is used for the writer when executing the template.
templenv uses text/template for generating the final file. Please review the official documentation for learning how to write those templates.
getEnv is a function for accessing environment variables from within templenv. For example, assuming you have a template snowman.tmpl with the following content:
My name is {{ getEnv "USER" }} and I like warm hugs!
and your current username is mario, by using templenv snowman.tmpl the following output will be generated:
My name is mario and I like warm hugs!
loadEnvFilename is a function for reading a file containing environment variables that then parses/converts them into what could look like Docker Compose environment variables.
For example, assuming you have two files, the first one a template docker-compose.tmpl with the following content:
version: '2'
services:
web:
image: mariocarrion/templenv:latest
command: /templenv
environment:
{{ loadEnvFilename " " "env.compose" }}
and the second one env.compose with the following content:
# Production env variables
HELLO=world!
The following output will be generated:
version: '2'
services:
web:
image: mariocarrion/templenv:latest
command: /templenv
environment:
HELLO: world!
You can use the included Dockerfile for building your own image, or if you prefer a smaller one you can use the Dockerfile.static, see DockerHub as well.