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.
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/v1.14.0/tmpl-linux-amd64
ARG TMPL_SHA256SUM=f05723257f684c03334a0809755274e066a100b64a972ecdbbac9451beadde05
RUN curl -fsSLo tmpl ${TMPL_URL} \
&& echo "${TMPL_SHA256SUM} tmpl" | sha256sum -c - \
&& chmod +x tmpl && mv tmpl /usr/local/bin/tmplTo 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=9a5124c3631028f5aa6ce96f02e645e408d097a2918bb535f05e4047c11eccf3
else
TMPL_SHA256SUM=f05723257f684c03334a0809755274e066a100b64a972ecdbbac9451beadde05
fi
TMPL_URL=https://github.com/tmc/tmpl/releases/download/v1.14.0/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_tmplGiven 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
Given a file 'b' with contents:
VERSION={{.HEAD}}
Invoking
$ cat b | HEAD="$(git rev-parse HEAD)" tmpl
Produces
VERSION=4dce1b0a03b59b5d63c876143e9a9a0605855748
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
😎