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https://github.com/cgmartin/envhandlebars
Substitutes environment variables in Handlebars templates, useful for configuration files in Docker
https://github.com/cgmartin/envhandlebars
config-template docker handlebars mustache-templates
Last synced: 1 day ago
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Substitutes environment variables in Handlebars templates, useful for configuration files in Docker
- Host: GitHub
- URL: https://github.com/cgmartin/envhandlebars
- Owner: cgmartin
- Created: 2016-03-15T13:56:15.000Z (almost 9 years ago)
- Default Branch: master
- Last Pushed: 2022-12-30T18:24:11.000Z (about 2 years ago)
- Last Synced: 2025-01-09T16:51:46.167Z (13 days ago)
- Topics: config-template, docker, handlebars, mustache-templates
- Language: JavaScript
- Size: 293 KB
- Stars: 16
- Watchers: 2
- Forks: 2
- Open Issues: 5
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
envhandlebars
=============
[](https://david-dm.org/cgmartin/envhandlebars)
[](http://badge.fury.io/js/envhandlebars)
[](https://travis-ci.org/cgmartin/envhandlebars)
A simple templating utility, akin to [`envsubst`](http://linuxcommand.org/man_pages/envsubst1.html), but using [Handlebars](http://handlebarsjs.com/) for more complex logic.
Environment variables are used as the data input to a Handlebars template:
```
$ export NAME=world
$ echo "Hello {{NAME}}" | envhandlebars
Hello world
```
This is particularly useful for dynamic configuration files in Docker containers and other [12-Factor applications](http://12factor.net/).
## Install
```
$ npm install -g envhandlebars
```
## Usage
Redirect a Mustache template file into stdin of `envhandlebars` and redirect the rendered stdout to a file:
```
Usage:
envhandlebars [options] < templatefile > renderedfile
Options:
--array-var-prefix="PRE_" process arrays only for vars with the specified prefix [Default: all]
--no-arrays disable variable name array processing
-h, --help print usage information
```
## Complex Examples
### Conditionals
Mustache conditionals can be used as is...
Template:
```
{{#if WORLD}}Hello {{WORLD}}{{/if}}!
```
Env vars:
```bash
WORLD=world
```
Output:
```
Hello world!
```
See the [if block helper](http://handlebarsjs.com/builtin_helpers.html#conditionals) docs page for more information.
### Iterators
Mustache iterators require using a special environment variable naming convention...
**Array of strings**
Template:
```
{{#each PEOPLE}}{{this}}{{#unless @last}}, {{/unless}}{{/each}}!
```
Env vars:
```bash
# Convention: {VARNAME}_{INDEX}
PEOPLE_0=Chris
PEOPLE_1=John
PEOPLE_2=Shayne
```
Output:
```
Chris, John, Shayne!
```
**Array of objects**
Template:
```
{{#each PEOPLE}}{{FIRST}} {{LAST}}{{#unless @last}}, {{/unless}}{{/each}}!
```
Env vars:
```bash
# Convention: {VARNAME}_{INDEX}_{PROPERTY}
PEOPLE_0_FIRST=Chris
PEOPLE_0_LAST=Martin
PEOPLE_1_FIRST=John
PEOPLE_1_LAST=Papa
PEOPLE_2_FIRST=Shayne
PEOPLE_2_LAST=Boyer
```
Output:
```
Chris Martin, John Papa, Shayne Boyer!
```
See the [each block helper](http://handlebarsjs.com/builtin_helpers.html#iteration) docs page for more information.
**NOTE:**
Some environments may have variables that conflict with this convention.
Use the `--array-var-prefix=FOO_` option to enable iterators only for variables that start with `FOO_`.
Alternatively, iterator parsing can be completely disabled with the `--no-arrays` option.
## Docker Usage
To generate configuration dynamically within a docker container, `envhandlebars` can be used before the main process starts. It can be done in the `CMD` or within a wrapper script.
Here is an example docker-compose.yml for a custom nginx container:
```
nginx:
build: .
volumes:
- ./mysite.template:/etc/nginx/conf.d/mysite.template
ports:
- "8080:80"
environment:
- NGINX_HOST=foobar.com
- NGINX_PORT=80
command: /bin/bash -c "envhandlebars < /etc/nginx/conf.d/mysite.template > /etc/nginx/conf.d/default.conf && nginx -g 'daemon off;'"
```
The mysite.template file may then contain variable references like this:
```
listen {{NGINX_PORT}};
```
You just need to make sure to install Node.js and envhandlebars (via npm) within your custom Dockerfile.
For debian-based images:
```
RUN apt-get update && apt-get install -y nodejs && npm i -g envhandlebars
```
For alpine-based images:
```
RUN apk add --update nodejs && npm i -g envhandlebars
```
## Custom Helpers or Partials
**(New in v1.3.0+)**
Custom Mustache helpers and partials can be implemented by extending the `envhandlebars` module with your own Node.js wrapper script:
```javascript
#!/usr/bin/env node
// Script: `myenvhandlebars`
'use strict';
var envhandlebars = require('envhandlebars');
// The Handlebars context is passed into this function
// for registering helpers, partials or other extensions.
function extendHandlebars(Handlebars) {
Handlebars.registerHelper('fullName', function(first, last) {
return last + ', ' + first;
});
}
envhandlebars({
extendHandlebars: extendHandlebars
});
```
See the [custom helpers](http://handlebarsjs.com/#helpers) docs page for more information.
## License
[MIT License](http://cgm.mit-license.org/)