112 lines
2.5 KiB
Markdown
112 lines
2.5 KiB
Markdown
---
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layout: "docs"
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page_title: "Configuring Variables"
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sidebar_current: "docs-config-variables"
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---
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# Variable Configuration
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Variables define the parameterization of Terraform configurations.
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Variables can be overridden via the CLI. Variable usage is
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covered in more detail in the
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[getting started guide](/intro/getting-started/variables.html).
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This page covers configuration syntax for variables.
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This page assumes you're familiar with the
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[configuration syntax](/docs/configuration/syntax.html)
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already.
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## Example
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A variable configuration looks like the following:
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```
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variable "key" {}
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variable "images" {
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default = {
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us-east-1 = "image-1234"
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us-west-2 = "image-4567"
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}
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}
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```
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## Description
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The `variable` block configures a single input variable for
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a Terraform configuration. Multiple variables blocks can be used to
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add multiple variables.
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The `NAME` given to the variable block is the name used to
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set the variable via the CLI as well as reference the variable
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throughout the Terraform configuration.
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Within the block (the `{ }`) is configuration for the variable.
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These are the parameters that can be set:
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* `default` (optional) - If set, this sets a default value
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for the variable. If this isn't set, the variable is required
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and Terraform will error if not set. The default value can be
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a string or a mapping. This is covered in more detail below.
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* `description` (optional) - A human-friendly description for
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the variable. This is primarily for documentation for users
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using your Terraform configuration. A future version of Terraform
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will expose these descriptions as part of some Terraform CLI
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command.
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------
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**Default values** can be either strings or maps. If a default
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value is omitted and the variable is required, the value assigned
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via the CLI must be a string.
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String values are simple and represent a basic key to value
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mapping where the key is the variable name. An example is:
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```
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variable "key" {
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default = "value"
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}
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```
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A map allows a key to contain a lookup table. This is useful
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for some values that change depending on some external pivot.
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A common use case for this is mapping cloud images to regions.
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An example:
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```
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variable "images" {
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default = {
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"us-east-1": "image-1234",
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"us-west-2": "image-4567",
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}
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}
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```
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The usage of maps, strings, etc. is documented fully in the
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[interpolation syntax](/docs/configuration/interpolation.html)
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page.
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## Syntax
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The full syntax is:
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```
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variable NAME {
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[default = DEFAULT]
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[description = DESCRIPTION]
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}
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```
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where `DEFAULT` is:
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```
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VALUE
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{
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KEY: VALUE,
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...
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}
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```
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