Variables

Rinse, Wash, Repeat (RWR) supports the use of variables and templating in blueprints to make them more dynamic and reusable. This page explains how to use variables and templating in your RWR blueprints.

Variables

Variables allow you to parameterize your blueprints and make them more flexible. RWR supports two types of variables:

1. User-defined variables

2. Built-in variables

User-defined Variables

User-defined variables are specified in the init.yaml file under the variables section. These variables can be referenced in your blueprints using the {{ .UserDefined.variable_name }} syntax.

Example init.yaml file:

variables:
  user_defined:
    app_version: 1.0.0
    server_port: 8080

In your blueprint:

packages:
  - name: myapp
    version: {{ .UserDefined.app_version }}

services:
  - name: myapp
    port: {{ .UserDefined.server_port }}

Built-in Variables

RWR provides a set of built-in variables that can be used in your blueprints. These variables are automatically populated based on the current system and configuration.

Variable	Description
{{ rwr.os }}	The operating system name (e.g., linux, macos, windows)
{{ rwr.arch }}	The system architecture (e.g., amd64, arm64)
{{ .User.username }}	The current user’s username
{{ .User.firstName }}	The current user’s First Name
{{ .User.lastName }}	The current user’s Last Name
{{ .User.fullName }}	The current user’s home directory
{{ .User.groupName }}	The current user’s Group Name (Linux/macOS Only)
{{ .User.home }}	The current user’s home directory
{{ .User.shell }}	The current user’s shell (e.g.; bash, zsh)
{{ .Flags.debug }}	Current Debug Flag Setting
{{ .Flags.logLevel }}	Current Log Level Setting
{{ .Flags.interactive }}	Current Interactive Mode setting
{{ .Flags.forceBootstrap }}	Current Force Bootstrap setting
{{ .Flags.ghAPIToken }}	Current Github API Token
{{ .Flags.sshKey }}	Current Private SSH Key (base64 encoded)
{{ .Flags.skipVersionCheck }}	Current Skip Version setting

Templating

RWR uses the Go template syntax for templating. You can use templating to conditionally include or exclude sections of your blueprints based on variable values or to generate dynamic content.

Conditional Sections

You can use the {{if}} and {{end}} directives to conditionally include or exclude sections of your blueprints.

Example:

packages:
  {{if eq rwr.os "linux"}}
  - name: git
    action: install
  {{end}}

  {{if eq rwr.os "macos"}}
  - name: homebrew
    action: install
  {{end}}

Looping

You can use the {{range}} and {{end}} directives to loop over a list of items.

Example:

packages:
  {{range .packages}}
  - name: {{.name}}
    version: {{.UserDefined.version}}
    action: {{.UserDefined.action}}
  {{end}}

Functions

RWR supports a subset of the Go template functions. Here are some commonly used functions:

Function	Description
{{eq arg1 arg2}}	Returns true if arg1 and arg2 are equal
{{ne arg1 arg2}}	Returns true if arg1 and arg2 are not equal
{{lt arg1 arg2}}	Returns true if arg1 is less than arg2
{{gt arg1 arg2}}	Returns true if arg1 is greater than arg2
{{join list separator}}	Joins a list of strings with the specified separator

For a complete list of supported functions, please refer to the Go template documentation.

Best Practices

• Use meaningful variable names that describe the purpose of the variable.

• Keep your templates simple and readable.

• Use variables to avoid hardcoding values in your blueprints.

• Use conditional sections to handle differences between operating systems or configurations.

• Test your templates thoroughly to ensure they work as expected.

By leveraging variables and templating in your RWR blueprints, you can create more flexible and reusable configurations that adapt to different environments and requirements.