tmpl

tmpl

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

tmpl is a single static binary with zero external dependencies that supplies the capabilities of many more complicated templating engines in less than 250 lines of Go code.

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
  -missingkey string
    	Controls behavior during execution if a map is indexed with a key that is not present in the map. Valid values are: default, zero, error (default "default")
  -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)
  -txtar
    	If true, output in txtar format instead of tar (only valid with -r)
  -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 template helpers compatible with sprig via an embedded, zero-dependency implementation.

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/v1.13/tmpl-linux-amd64
ARG TMPL_SHA256SUM=929d40ba862bc0ee91e6d1259595e93f1209ac0f513597b49107f963c3455ca7
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 [[ "${platform}" == "darwin" ]]; then
    TMPL_SHA256SUM=fb21eb116f8e31679a0f316069dcf9580a0800bc0e3967d1ffe3f5a5d599ad23
  else
    TMPL_SHA256SUM=929d40ba862bc0ee91e6d1259595e93f1209ac0f513597b49107f963c3455ca7
  fi
  TMPL_URL=https://github.com/tmc/tmpl/releases/download/v1.13/tmpl-${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
😎