String interpolation in Terraform - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is string interpolation in Terraform?

String interpolation in Terraform is a way to insert the value of variables or expressions inside a string by using ${} syntax.

beginner

How do you include a variable named 'region' inside a string in Terraform?

You write the string with ${var.region} where you want the variable's value to appear, for example: "The region is ${var.region}".

intermediate

Can you use expressions inside Terraform string interpolation? Give an example.

Yes, you can use expressions. For example: "${var.count > 1 ? \"many\" : \"one\"}" will insert "many" if count is greater than 1, otherwise "one".

beginner

What happens if you write a string without ${} in Terraform?

Terraform treats it as a plain string with no variable substitution or expression evaluation.

beginner

Why is string interpolation useful in Terraform configurations?

It lets you build dynamic strings that change based on variables or resource attributes, making your infrastructure code flexible and reusable.

How do you write string interpolation for a variable named 'name' in Terraform?

A "var.name"

B "$var.name"

C "{var.name}"

D "${var.name}"

Terraform uses ${} to interpolate variables inside strings, so "${var.name}" is correct.

What will Terraform output for the string: "Hello, ${var.user}!" if var.user is "Alice"?

A Hello, Alice!

B Hello, ${var.user}!

C Hello, var.user!

D Hello, !

Terraform replaces ${var.user} with the value "Alice" inside the string.

Can you use arithmetic inside Terraform string interpolation like "${var.count + 1}"?

A Yes, expressions are allowed inside ${}.

B No, only variables are allowed.

C Only strings can be interpolated.

D You must use a separate variable for calculations.

Terraform supports expressions inside ${}, including arithmetic.

What is the correct way to write a literal dollar sign in a Terraform string without interpolation?

A "\$"

B "$"

C "$$"

D "${dollar}"

Using double dollar signs "$$" escapes the dollar sign to appear literally.

If you write "The value is var.value" without ${}, what happens?

A Terraform replaces var.value with its value.

B Terraform treats it as plain text with no substitution.

C Terraform throws an error.

D Terraform ignores the string.

Without ${}, Terraform does not interpolate and treats the string as plain text.

Explain how string interpolation works in Terraform and why it is useful.

Think about how you can build strings that change based on variables.

Describe how to include a variable and an expression inside a Terraform string using interpolation.

Use ${} to insert both simple variables and calculations.