tmpl

tmpl

This is a small program to render files using Go templates. It takes files (or stdin) as input, an optional values YAML file and outputs one rendered document to stdout. The bulk of the available functions to tmpl comes from the sprig module.

This program has a lot of alternatives, most with the same name (look at me being original). Please consider looking into those projects. I wrote this because I wanted a slim program with few dependencies that follows the Unix philosophy of "do one thing and one thing well". I also wanted certain behaviour and functions.

WARNING: This utility should not be used in a production environment, use at your own risk. This is an immature project. Anything can change, at any moment.

Installation

For now, installing is only supported via the Go toolchain:

go install github.com/bdazl/tmpl@latest

Usage

The most basic use-case is reading from stdin:

$ echo 'My home: {{ env "HOME" }}' | tmpl
My home: /home/bdazl

The utility is designed to render one document, but you may want to combine documents (and share definitions):

$ tmpl tmpl/tmpl.t tmpl/info.t
  _    __  __ ,___  _
 | |  /  \/  \  _ \| |
<   > | |\/| | |_) | |
 | |__| |  | |  __/| |__
 \___/|_|  |_|_|   \___/

version: v0.1.0

The order of the rendered document is very important, because go templates only lets you make definitions at the start (the initial document(s)):

$ tmpl tmpl/info.t tmpl/tmpl.t
error: template: tmpl:1:12: executing "tmpl" at <{{template "tmpl.banner"}}>: template "tmpl.banner" not defined

Data

Values can be sourced from a YAML-file. Per default they exists within the root scope (.). In the following example, values are sourced from tmpl/data.yml and placed in the data root. We use the tmpl.version value to render the template:

$ echo "{{ .tmpl.version }}" | tmpl -d tmpl/data.yml
v0.1.0

To define the root, use the -r flag:

$ echo "{{ .Values.tmpl.version }}" | tmpl -d tmpl/data.yml -r Values
v0.1.0

Functions

Most of the available functions to tmpl comes from the sprig module (implementation details here).

In addition to these functions, tmpl defines its own:

• run: run arbitrary commands and return the combined stdout and stderr (ignores error codes).
• runErr: similar to run, but if exit code is non-zero (or other error) the error will be printed.
• exitCode: run command, but return only its exit code

Some functions mimic Helm, and these are implemented and works similarly to how they work in Helm:

• toYaml, fromYaml, fromYamlArray, toJson, fromJson, fromJsonArray

The following functions are available, but not yet implemented:

• include, tpl, required and lookup