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https://github.com/noqcks/gucci

Templating on the command line with sprig.
https://github.com/noqcks/gucci

binary cli-templating golang golang-binaries sprig

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Templating on the command line with sprig.

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# Gucci



A simple CLI templating tool written in golang.



[![GitHub version](https://badge.fury.io/gh/noqcks%2Fgucci.svg)](https://badge.fury.io/gh/noqcks%2Fgucci)



## 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=1.6.13

wget -q "https://github.com/noqcks/gucci/releases/download/v${VERSION}/gucci-v${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:



```bash

$ gucci

Start typing stuff {{ print "here" }}

^d

Start typing stuff here

```



Via piping:



```bash

$ echo '{{ html "" }}' | 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:



```yaml

# vars.yaml

hosts:

  - name: bastion

  - name: app

```



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



```bash

$ gucci -f vars.yaml template.tpl

```



#### Environment Variables



Here, `MY_HOST` is available to the template:



```bash

$ export MY_HOST=localhost

$ gucci template.tpl

```



#### Variable Options



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



```bash

$ 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:



```yaml

foo:

  bar: baz

```



## Templating



### Options



Existing [golang templating options](https://golang.org/pkg/text/template/#Template.Option) 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`:



```tpl

# 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:



```yaml

# 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`:



```shell

$ 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](https://golang.org/pkg/text/template/#hdr-Functions) are available for use.



### Sprig Functions



gucci ships with the [sprig templating functions library](http://masterminds.github.io/sprig/) offering a wide variety of template helpers.



### 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:



```bash

go get github.com/noqcks/gucci

go get github.com/onsi/ginkgo/ginkgo

go get github.com/onsi/gomega

```



Run tests:



```bash

ginkgo ./...

```