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Gucci

A simple CLI templating tool written in golang.

GitHub version License Build Status

Installation

If you have go installed:

$ go get github.com/noqcks/gucci

Or you can just download the binary and move it into your PATH:

VERSION=1.4.0
wget -q https://github.com/noqcks/gucci/releases/download/${VERSION}/gucci-v${VERSION}-darwin-amd64
chmod +x gucci-v${VERSION}-darwin-amd64
mv gucci-v${VERSION}-darwin-amd64 /usr/local/bin/gucci

Use

Locating Templates

gucci can locate a template in multiple ways.

File

Pass the template file path as the first argument:

$ gucci template.tpl > template.out

Stdin

Supply the template through standard input:

$ gucci
Start typing stuff {{ print "here" }}
^d
Start typing stuff here

Via piping:

$ echo '{{ html "<escape-me/>" }}' | gucci

Supplying Variable Inputs

gucci can receive variables for use in templates in the following ways (in order of lowest to highest precedence):

  • A JSON or YAML file
  • Environment variables
  • Variable command options

Variables File

Given an example variables file:

# vars.yaml
hosts:
  - name: bastion
  - name: app

Pass it into gucci with -f or --vars-file:

$ gucci -f vars.yaml template.tpl

Environment Variables

Here, MY_HOST is available to the template:

$ export MY_HOST=localhost
$ gucci template.tpl

Variable Options

Pass variable options into gucci with -s or --set-var, which can be repeated:

$ gucci -s foo.bar=baz template.tpl

Variable option keys are split on the . character, and nested such that the above example would equate to the following yaml variable input:

foo:
  bar: baz

Templating

Options

Existing golang templating options can be used for templating.

If no option is specified, the missingkey=error option will be used (execution stops immediately with an error if a key used in the template is not present in the supplied values).

One might want a different value for missingkey when using conditionals and having keys that won't be used at all.

For instance, given the following template, containing two docker-compose services service1 and service2:

# template.tpl
version: "3.8"

services:
{{- if .service1 }}
  service1:
    image: {{ .service1.image }}
    restart: "always"
    ports: {{ toYaml .service1.ports | nindent 6}}
{{- end }}
{{- if .service2 }}
  service2:
    image: {{ .service2.image }}
    restart: "unless-stopped"
    ports: {{ toYaml .service2.ports | nindent 6}}
{{- end }}

And imagine a scenario where whe only need service2. By using the following values file:

# values.yaml
service2:
  image: "myservice:latest"
  ports:
    - "80"
    - "443"

And using a different missingkey=error, we can actually get the desired result without having to define the values for service1:

$ gucci -o missingkey=zero -f values.yaml  template.tpl
version: "3.8"

services:
  service2:
    image: myservice:latest
    restart: "unless-stopped"
    ports:
      - "80"
      - "443"

GoLang Functions

All of the existing golang templating functions are available for use.

Sprig Functions

gucci ships with the sprig templating functions library offering a wide variety of template helpers. Sprig's env and expandenv functions are disabled in favor of gucci's own environment variable parsing (see below).

Built In Functions

Furthermore, this tool also includes custom functions:

  • shell: For arbitrary shell commands

    {{ shell "echo hello world" }}
    

    and

    # guest: world
    {{ shell "echo hello " .guest }}
    

    Both produce:

    hello world
    
  • toYaml: Print items in YAML format

    {{ $myList := list "a" "b" "c" }}
    {{ toYaml $myList }}
    

    Produces:

    - a
    - b
    - c
    

Example

NOTE: gucci reads and makes available all environment variables.

For example a var $LOCALHOST = 127.0.0.1

gucci template.tpl > template.conf

# template.tpl
{{ .LOCALHOST }}

gucci template.tpl > template.conf -->

# template.conf
127.0.0.1

simple enough!

For an iteration example, you have $BACKENDS=server1.com,server2.com

# template.tpl
{{ range split .BACKENDS "," }}
server {{ . }}
{{ end }}

gucci template.tpl > template.conf -->

# template.conf
server server1.com
server server2.com

Testing

Setup:

go get github.com/noqcks/gucci
go get github.com/onsi/ginkgo/ginkgo
go get github.com/onsi/gomega

Run tests:

ginkgo ./...