tmpl

Command tmpl renders a template with the current env vars as input.

tmpl packs a punch in under 200 lines of code: a single static binary supplies the capabilities of many more complicated templating engines.

It's especially helpful as an early entrypoint into containers to prepare configuration files.

$ tmpl -h
Usage of tmpl:
  -f string
    	Input source (default "-")
  -html
    	If true, use html/template instead of text/template
  -r string
    	If provided, traverse the argument as a directory
  -stripn int
    	If provided, strips this many directories from the output (only valid if -r and -w are provided)
  -w string
    	Output destination (default "-")

It effectively exposes Go's text/template for use in shells.

Reference text/template documentation for template language specification.

It includes all of the template helpers from sprig.

Safe Dockerfile Inclusion

To safely include in your build pipelines:

FROM ubuntu:bionic

RUN apt-get update
RUN apt-get install -y curl

ARG TMPL_URL=https://github.com/tmc/tmpl/releases/download/v1.11/tmpl_linux_amd64
ARG TMPL_SHA256SUM=80b2c20c4c5fa6352d962b6a8dee406652e61153fa1afb520a4d51eb3eb0e0f7
RUN curl -fsSLo tmpl ${TMPL_URL} \
		&& echo "${TMPL_SHA256SUM}  tmpl" | sha256sum -c - \
		&& chmod +x tmpl && mv tmpl /usr/local/bin/tmpl

Safe Shell Scripting Inclusion

To safely include in your shell scripts:

#!/bin/bash
set -euo pipefail

# Helper Functions
case "${OSTYPE}" in
linux*) platform=linux
	;;
darwin*)
	platform=darwin
	;;
*) platform=unknown ;;
esac

function install_tmpl() {
  if [[ "${platform}" == "darwin" ]]; then
    TMPL_SHA256SUM=6325565b39c02cdf39f4eba8ac127013dc96e4d365192fc57c65d3c7c8cb027f
  else
    TMPL_SHA256SUM=80b2c20c4c5fa6352d962b6a8dee406652e61153fa1afb520a4d51eb3eb0e0f7
  fi
  TMPL_URL=https://github.com/tmc/tmpl/releases/download/v1.11/tmpl_${platform}_amd64
  curl -fsSLo tmpl ${TMPL_URL} \
    && echo "${TMPL_SHA256SUM}  tmpl" | sha256sum -c - \
    && chmod +x tmpl
  mv tmpl /usr/local/bin/tmpl || echo "could not move tmpl into place"
}

command -v tmpl > /dev/null || install_tmpl

Example 1

Given a file 'a' with contents:

{{ range $key, $value := . }}
  KEY:{{ $key }} VALUE:{{ $value }}
{{ end }}

Invoking

$ cat a | env -i ANSWER=42 ITEM=Towel `which tmpl`

Produces

KEY:ANSWER VALUE:42

KEY:ITEM VALUE:Towel

Example 2

Given a file 'b' with contents:

VERSION={{.HEAD}}

Invoking

$ cat b | HEAD="$(git rev-parse HEAD)" tmpl

Produces

VERSION=4dce1b0a03b59b5d63c876143e9a9a0605855748

Example 3

Given a directory via the -r flag, tmpl recurses, expanding each path and file and produces a tarball to the output destination.

Invoking

$ mkdir testdata/recursive-out
$ tmpl -r testdata/recursive-example | tar -C testdata/recursive-out --strip-components=2 -xvf -
$ cat testdata/recursive-out/user-tmc

Produces (for me, at time of writing)

For the current user tmc:
Shell: /bin/bash
EDITOR: vim
😎