datasubst

A simple go template based tool that supports JSON, YAML and environment variables as data sources.

This tool has been written as an alternative to envsubst in order to support additional data source formats, such as YAML and JSON files. Since it is powered by go template, built-in functions, loops, conditionals and more can be used for extra flexibility.

Installation

On macOS or Linux, a Homebrew formula is available:

brew tap marcelocarlos/tap
brew install datasubst

Alternatively, you can install a development version using:

go get github.com/marcelocarlos/datasubst

If you don't want to install it, you can run datasubst via Docker instead:

docker run --rm ghcr.io/marcelocarlos/datasubst:v0

GitHub Action

There is also a setup-datasubst action available so you can use datasubst in your GitHub Actions workflow. To use it, just add the following step in you workflow:

- name: Setup datasubst
  uses: marcelocarlos/setup-datasubst@v1
  with:
    version: v0.7.0

Usage

# Using JSON as data source
datasubst --json-data examples/basic-data.json -i examples/basic-input.txt
# Using YAML as data source
datasubst --yaml-data examples/basic-data.yaml -i examples/basic-input.txt
# Using environment variables as data source
TEST1="hello" TEST2="world" datasubst --input examples/basic-input-env.txt --env-data

# Using stdin - JSON
echo "v1: {{ .key1 }}" | datasubst --json-data examples/basic-data.json
# Using stdin - YAML
echo "v3: {{ .key2.first.key3 }}" | datasubst --yaml-data examples/basic-data.yaml
# Using stdin - env
echo "{{ .TEST1 }} {{ .TEST2 }}" | TEST1="hello" TEST2="world" datasubst --env-data

# Specifying JSON subtrees to use (available for JSON and YAML)
echo "{{ .first.key3 }}" | datasubst --json-data examples/basic-data.json --subtree .key2
# Specifying YAML subtrees to use (available for JSON and YAML)
datasubst --json-data examples/basic-data.json --subtree .key2 -i examples/basic-input-subtree.txt

# Using additional options, such -s (strict mode) and -d (change delimiters)
echo "(( .TEST ))" | TEST="hi" datasubst --env-data -d '((:))' -s

See examples for more.

Build from source

go build -ldflags=-X=main.Version=$(git describe --tags)