97 lines
2.9 KiB
Markdown
97 lines
2.9 KiB
Markdown
---
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layout: "language"
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page_title: "Local Values - 0.11 Configuration Language"
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sidebar_current: "docs-conf-old-locals"
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description: |-
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Local values assign a name to an expression that can then be used multiple times
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within a module.
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---
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# Local Values
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-> **Note:** This page is about Terraform 0.11 and earlier. For Terraform 0.12
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and later, see
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[Configuration Language: Configuring Local Values](../configuration/locals.html).
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Local values assign a name to an expression, that can then be used multiple
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times within a module.
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Comparing modules to functions in a traditional programming language,
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if [variables](./variables.html) are analogous to function arguments and
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[outputs](./outputs.html) are analogous to function return values then
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_local values_ are comparable to a function's local variables.
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This page assumes you're already familiar with
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[the configuration syntax](./syntax.html).
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## Examples
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Local values are defined in `locals` blocks:
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```hcl
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# Ids for multiple sets of EC2 instances, merged together
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locals {
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instance_ids = "${concat(aws_instance.blue.*.id, aws_instance.green.*.id)}"
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}
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# A computed default name prefix
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locals {
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default_name_prefix = "${var.project_name}-web"
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name_prefix = "${var.name_prefix != "" ? var.name_prefix : local.default_name_prefix}"
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}
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# Local values can be interpolated elsewhere using the "local." prefix.
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resource "aws_s3_bucket" "files" {
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bucket = "${local.name_prefix}-files"
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# ...
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}
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```
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Named local maps can be merged with local maps to implement common or default
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values:
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```hcl
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# Define the common tags for all resources
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locals {
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common_tags = {
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Component = "awesome-app"
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Environment = "production"
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}
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}
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# Create a resource that blends the common tags with instance-specific tags.
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resource "aws_instance" "server" {
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ami = "ami-123456"
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instance_type = "t2.micro"
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tags = "${merge(
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local.common_tags,
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map(
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"Name", "awesome-app-server",
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"Role", "server"
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)
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)}"
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}
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```
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## Description
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The `locals` block defines one or more local variables within a module.
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Each `locals` block can have as many locals as needed, and there can be any
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number of `locals` blocks within a module.
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The names given for the items in the `locals` block must be unique throughout
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a module. The given value can be any expression that is valid within
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the current module.
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The expression of a local value can refer to other locals, but as usual
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reference cycles are not allowed. That is, a local cannot refer to itself
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or to a variable that refers (directly or indirectly) back to it.
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It's recommended to group together logically-related local values into
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a single block, particularly if they depend on each other. This will help
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the reader understand the relationships between variables. Conversely,
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prefer to define _unrelated_ local values in _separate_ blocks, and consider
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annotating each block with a comment describing any context common to all
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of the enclosed locals.
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