template

template

Template is a thin wrapper on text/template, the golang templating engine. The primary usecase for the utility is to dynamically modify config templates.

Usage

Typical usage is to read a file and apply a couple variables.

Example Template (ingress.yml.template):

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: {{ .Var "service" }}
  ref: {{ .Env "CURRENT_REF" }}

If we then run the following:

> CURRENT_REF="abcdef" template -f ingress.yml.template --var service="my service"

template will then print to the screen the updated template:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: my service
  ref: abcdef

You can alternately read from stdin by omitting the -f flag.

Commandline Flag Reference

-f <TEMPLATE PATH>

The -f flag specifies an input file. If in the form -f - template will read the file from stdin.

-i <TEMPLATE PATH>

The -i flag specifies an addition template file referencable in the master template.

-vars <VARS PATH[.json|(.yml|.yaml|*)]>

The -vars flag specifies an input file with variable definitions. If the filename is .json it will be unmarshalled as json, otherwise it will be unmarshalled as yaml.

-var <KEY>=<VALUE>

The -var flag specifies a variable for the template.

-o <OUTPUT PATH>

The -o flag specifies an output path. If not present, output will be piped to stdout.

-delims "<LEFT DELIMITER>,<RIGHT DELIMITER>

The -delims flag specifies the left and right delimiters for template action, defaults to {{,}}.

Template Function Reference

.Env

Env will return an environment variable. It takes the environment variable name as the first parameter. It can take a default value as a second parameter. If no default is specified, and the environment variable is not present, this will cause an error.

{{ .Env "<var name>" }}

With a default:

{{ .Env "<var name>" "<default value>" }}

.Var

Var will return a variable as set by the commandline. It takes the variable name as the first parameter. It can take a default value as a second parameter. If no default is specified, and the variable is not present, this will cause an error.

{{ .Var "<var name>" }}

With a default:

{{ .Var "<var name>" <default value> }}

Note: Var differs from Env in that var values can be any type, not just strings.

.File

File will return the contents of a given file and inline those contents into the config. Note; the contents of this file will not be processed by the template interpreter, they will appear in the final output as they did on disk.

{{ .File "<file path>" }}

Template pipeline helpers

Template ships with a number of pipeline helpers that can be used with the output of .Var, .Env and even .File.

text/template Reference

More information about the text/template template language can be found here: text template