website: configuration

website/source/docs/configuration/interpolation.html.md

@@ -0,0 +1,42 @@
+---
+layout: "docs"
+page_title: "Interpolation Syntax"
+sidebar_current: "docs-config-interpolation"
+---
+
+# Interpolation Syntax
+
+Embedded within strings in Terraform, whether you're using the
+Terraform syntax or JSON syntax, you can interpolate other values
+into strings. These interpolations are wrapped in `${}`, such as
+`${var.foo}`.
+
+The interpolation syntax is powerful and allows you to reference
+variables, attributes of resources, call functions, etc.
+
+To reference variables, use the `var.` prefix followed by the
+variable name. For example, `${var.foo}` will interpolate the
+`foo` variable value. If the variable is a mapping, then you
+can reference static keys in the map with the syntax
+`var.MAP.KEY`. For example, `${var.amis.us-east-1}` would
+get the value of the `us-east-1` key within the `amis` variable
+that is a mapping.
+
+To reference attributes of other resources, the syntax is
+`TYPE.NAME.ATTRIBUTE`. For example, `${aws_instance.web.id}`
+will interpolate the ID attribute from the "aws\_instance"
+resource named "web".
+
+Finally, Terraform ships with built-in functions. Functions
+are called with the syntax `name(arg, arg2, ...)`. For example,
+to read a file: `${file("path.txt")}`. The built-in functions
+are documented below.
+
+## Built-in Functions
+
+The supported built-in functions are:
+
+  * `file(path)` - Reads the contents of a file into the string.
+
+  * `lookup(map, key)` - Performs a dynamic lookup into a mapping
+      variable.

website/source/docs/configuration/load.html.md

@@ -8,9 +8,13 @@ sidebar_current: "docs-config-load"
 
 When invoking any command that loads the Terraform configuration,
 Terraform loads all configuration files within the directory
-specified in alphabetical order. The flies loaded must end in
+specified in alphabetical order.
+
+The files loaded must end in
 either `.tf` or `.tf.json` to specify the format that is in use.
-Otherwise, the files are ignored.
+Otherwise, the files are ignored. Multiple file formats can
+be present in the same directory; it is okay to have one Terraform
+configuration file be Terraform syntax and another be JSON.
 
 [Override](/docs/configuration/override.html)
 files are the exception, as they're loaded after all non-override

website/source/docs/configuration/override.html.md

@@ -0,0 +1,52 @@
+---
+layout: "docs"
+page_title: "Overrides"
+sidebar_current: "docs-config-override"
+---
+
+# Overrides
+
+Terraform loads all configuration files within a directory and
+appends them together. Terraform also has a concept of _overrides_,
+a way to create files that are loaded last and _merged_ into your
+configuration, rather than appended.
+
+Overrides have a few use cases:
+
+  * Machines (tools) can create overrides to modify Terraform
+    behavior without having to edit the Terraform configuration
+    tailored to human readability.
+
+  * Temporary modifications can be made to Terraform configurations
+    without having to modify the configuration itself.
+
+Overrides names must be `override` or end in `_override`, excluding
+the extension. Examples of valid override files are `override.tf`,
+`override.tf.json`, `temp_override.tf`.
+
+Override files are loaded last in alphabetical order.
+
+Override files can be in Terraform syntax or JSON, just like non-override
+Terraform configurations.
+
+## Example
+
+If you have a Terraform configuration `example.tf` with the contents:
+
+```
+resource "aws_instance" "web" {
+    ami = "ami-1234567"
+}
+```
+
+And you created a file `override.tf` with the contents:
+
+```
+resource "aws_instance" "web" {
+    ami = "foo"
+}
+```
+
+Then the AMI for the one resource will be replaced with "foo". Note
+that the override syntax can be Terraform syntax or JSON. You can
+mix and match syntaxes without issue.

website/source/docs/configuration/syntax.html.md

@@ -47,6 +47,11 @@ Basic bullet point reference:
 
   * Strings are in double-quotes.
 
+  * Strings can interpolate other values using syntax wrapped
+    in `${}`, such as `${var.foo}`. The full syntax for interpolation
+    is
+    [documented here](/docs/configuration/interpolation.html).
+
   * Numbers are assumed to be base 10. If you prefix a number with
     `0x`, it is treated as a hexadecimal number.
 

website/source/layouts/docs.erb

@@ -17,6 +17,10 @@
 					<a href="/docs/configuration/syntax.html">Configuration Syntax</a>
 					</li>
 
+					<li<%= sidebar_current("docs-config-interpolation") %>>
+					<a href="/docs/configuration/interpolation.html">Interpolation Syntax</a>
+					</li>
+
 					<li<%= sidebar_current("docs-config-override") %>>
 					<a href="/docs/configuration/override.html">Overrides</a>
 					</li>