How to Check if a Variable String Matches Two Values in Terraform

Discover effective solutions for checking a variable string against multiple values in `Terraform`. Learn best practices and techniques to avoid common errors.
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How to Check if a Variable String Matches Two Values in Terraform

When working with Terraform, you may encounter situations where you need to verify whether a variable string matches one of multiple acceptable values. This task might sound straightforward, but it can lead to frustrating errors if not approached correctly.

In this guide, we will discuss how to effectively compare a variable string against two values and provide solutions that ensure your Terraform code runs smoothly without errors.

The Problem

In the example you might have seen, a piece of code was being used to check if a variable, var.vnet_type, was either "External" or "Internal":

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When attempting to execute this code, Terraform throws the following error message:

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The error indicates an issue with the logical comparison. The construct var.vnet_type == "External" || "Internal" is not valid in Terraform.

The Solution

To effectively check if a variable string matches more than one value, you have two solid options.

Method 1: Direct Comparison

Rather than using the combined comparison, you can explicitly compare var.vnet_type to each value:

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This method provides clarity and directly targets your variable against each of the acceptable values, ensuring that Terraform understands your intent.

Method 2: Using a List

If you want to simplify your comparisons and reduce repetition, you can use a list to define acceptable values and check if the variable is included in that list:

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This strategy is particularly useful if you have more than two values to check against. It allows for cleaner code and minimizes the risk of syntax errors.

Summary

To summarize, here are the two approaches to check if a variable string matches multiple values in Terraform:

Direct Comparison:

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List Checking:

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Both methods ensure that your code is robust and error-free. By following these practices, you'll avoid the common pitfalls associated with Terraform variable comparisons.

If you have encountered similar problems, feel free to share your thoughts or ask questions in the comments below!

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