Terraform

How to Use the If / Else Statement in Terraform – Examples

Terraform IF Statement

In this short article, we will take a look at the Terraform if statement (hint, it doesn’t exist) and look at a few examples. Let’s dive in!

Conditional Expressions in Terraform

condition ? true_val : false_val

Example 1

For example, the statement below checks if the variable var.serveris set to “UbuntuServer”. If it is true, then count = 0 and will be deployed zero times. If it is set to anything else, then count = 1, and the resource will be deployed 1 time.

Note that Terraform does support traditional logical, equality, and comparison operators such as == (equal to) or != (not equal to) && (and), etc. These operators can be added together to make more complex conditionals.

count = var.server == "UbuntuServer" ? 0 : 1

Example 2

Another common use of conditional expressions is to define defaults to replace invalid values. The example below checks if the variable var.server is an empty string. If it is, then the value is “MicrosoftWindowsServer”. If not, then it is the actual value of var.server .

var.server != "" ? var.server : "MicrosoftWindowsServer"

Example 3

When creating a conditional expression, the two result types can be of any type. In the example below, we have an integer of 100 if the condition is true, and a string “UbuntuServer” if the condition is false.

var.server ? 100 : "UbuntuServer"

However, this can cause confusion as Terraform will attempt to find a type that they can both convert to and make those conversions automatically if so. In the above case, both can be converted to a String.

To avoid this, writing the condition with a specific conversion function is recommended (see below using the toString function):

var.server ? tostring(100) : "UbuntuServer"

Terraform Coalesce Function

locals{
  dev    = var.environment == "DEV" ? "uksouth" : ""
  uit 	 = var.environment == "UIT" ? "ukwest" : ""
  prod 	 = var.environment != "PROD" && var.environment != "UIT" ? "useast2" : ""
  region = coalesce(local.dev, local.uit, local.prod)
}

Key Points

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