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clarify local and input variables (#12334)

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* clarify local and input variables

* Apply suggestions from code review

Co-authored-by: Rose M Koron <32436232+rkoron007@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Rose M Koron <32436232+rkoron007@users.noreply.github.com>
Co-authored-by: Wilken Rivera <wilken@hashicorp.com>

* Apply suggestions from code review

Co-authored-by: Wilken Rivera <wilken@hashicorp.com>

---------

Co-authored-by: Rose M Koron <32436232+rkoron007@users.noreply.github.com>
Co-authored-by: Wilken Rivera <wilken@hashicorp.com>
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Alan Szlosek Jr 2023-04-12 18:05:29 -04:00 committed by GitHub
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29
website/content/docs/templates/hcl_templates/locals.mdx vendored
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@ -1,35 +1,34 @@
---
page_title: Local Values - HCL Configuration Language
page_title: Local Variables - HCL Configuration Language
description: >-
Local values assign a name to an expression that can then be used multiple
Local variables assign a name to an expression that you can use multiple
times within a folder.
---
# Local Values
# Local Variables
`@include 'from-1.5/beta-hcl2-note.mdx'`
There are two kinds of variables in HCL Packer templates: Input variables,
sometimes simply called "variables", and Local variables, also known as
"locals". Input variables may have defaults, but those defaults can
be overridden from the command line or special variable files. Local variables
can be thought of as constants, and are not able to be overridden at runtime.
"locals". Input variables may have defaults, but those defaults can be
overridden using command line options, environment variables, or variable
definitions files. Local variables can not be overridden.
This page is about local variables. To learn about input variables, see the
[input variables](/packer/docs/templates/hcl_templates/variables) page.
Local values assign a name to an expression, that can then be used multiple
times within a folder.
If [variables](/packer/docs/templates/hcl_templates/variables) are analogous to function arguments then
_local values_ are comparable to a function's local variables.
Local variables assign a name to an expression, which you can use multiple
times within a folder. The expression is evaluated at run time, and can
reference input variables, other local variables, data sources, and HCL
functions.
Input variable and local variable usage are introduced in the [_Variables
Guide_](/packer/guides/hcl/variables).
## Examples
Local values are defined in `local` or `locals` blocks:
Local variables are defined in a `local` or `locals` block:
```hcl
# Using the local block allows you to mark locals as sensitive, which will
@ -51,7 +50,7 @@ locals {
name_prefix = "${var.name_prefix != "" ? var.name_prefix : local.default_name_prefix}"
}
# Local values can be interpolated elsewhere using the "local." prefix.
# Local variables can be referenced using the "local." prefix.
source "virtualbox-iso" "example" {
output = "${local.name_prefix}-files"
# ...
@ -120,10 +119,10 @@ The expression of a local value can refer to other locals, but reference cycles
are not allowed. That is, a local cannot refer to itself or to a variable that
refers (directly or indirectly) back to it.
It's recommended to group together logically-related local values into a single
It's recommended to group together logically-related local variables into a single
block, particularly if they depend on each other. This will help the reader
understand the relationships between variables. Conversely, prefer to define
_unrelated_ local values in _separate_ blocks, and consider annotating each
_unrelated_ local variables in _separate_ blocks, and consider annotating each
block with a comment describing any context common to all of the enclosed
locals.

10
website/content/docs/templates/hcl_templates/variables.mdx vendored
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@ -11,9 +11,10 @@ description: |-
There are two kinds of variables in HCL Packer templates: Input variables,
sometimes simply called "variables", and Local variables, also known as
"locals". Input variables may have defaults, but those defaults can
be overridden from the command line or special variable files. Local variables
can be thought of as constants, and are not able to be overridden at runtime.
"locals". Input variables may have defaults, but those defaults can be
overridden using command line options, environment variables, or variable
definitions files. However, nothing can change the value of an input variable
after the initial override.
This page is about input variables. To learn about local variables, see the
[locals](/packer/docs/templates/hcl_templates/locals) page.
@ -21,9 +22,6 @@ This page is about input variables. To learn about local variables, see the
Input variables serve as parameters for a Packer build, allowing aspects of the
build to be customized without altering the build's own source code.
When you declare variables in the build of your configuration, you can set
their values using CLI options and environment variables.
Input variable and local variable usage are introduced in the [_Variables
Guide_](/packer/guides/hcl/variables).