File functions (file, templatefile) in Terraform - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

Output of file() function reading a text file

Given a file named message.txt containing the text Hello, Terraform!, what will be the output of the following Terraform expression?

file("message.txt")

A null

B "Hello, Terraform!"

C SyntaxError

D "file(message.txt)"

💡 Hint

The file() function reads the entire content of a file as a string.

The file() function returns the exact content of the file as a string. Since the file contains 'Hello, Terraform!', that string is returned.

❓ Configuration

intermediate

Using templatefile() with variables

Consider a template file greeting.tmpl with content:

Hello, ${name}!

Which Terraform expression correctly renders this template with the variable name set to "Alice"?

A templatefile("greeting.tmpl", { name = "Alice" })

B templatefile("greeting.tmpl", ["name", "Alice"])

C templatefile("greeting.tmpl", name = "Alice")

D templatefile("greeting.tmpl", { "name": "Alice" })

💡 Hint

templatefile() expects a map of variable names to values.

templatefile() requires the second argument to be a map with keys matching template variables. Option A correctly provides a map with key 'name' and value 'Alice'.

🧠 Conceptual

advanced

Behavior of file() with a missing file

What happens when Terraform runs the expression file("missing.txt") but the file missing.txt does not exist in the working directory?

A Terraform returns an empty string ""

B Terraform creates an empty file named missing.txt

C Terraform raises a runtime error and stops execution

D Terraform returns null

💡 Hint

Terraform expects the file to exist when using file().

If the file does not exist, Terraform raises an error and stops because it cannot read the file content.

❓ security

advanced

Security risk of using templatefile() with untrusted input

Why is it risky to use templatefile() with variables that come directly from user input without validation?

A It can lead to injection of malicious code into generated configuration files

B It can cause Terraform to crash due to syntax errors in the template

C It will automatically sanitize the input, so no risk exists

D It causes Terraform to ignore the variables and use defaults

💡 Hint

Untrusted input can alter the output in unexpected ways.

Using unvalidated user input in templates can inject harmful content, causing security vulnerabilities in generated infrastructure code.

❓ Architecture

expert

Choosing between file() and templatefile() for configuration generation

You need to generate multiple configuration files with dynamic values for a large infrastructure project. Which approach is best to maintain clarity, reusability, and ease of updates?

A Embed all configuration content directly in Terraform variables as strings

B Use file() to read static files and manually replace variables in Terraform code

C Use file() to read templates and parse them with external scripts outside Terraform

D Use templatefile() with parameterized templates to generate files dynamically

💡 Hint

Think about maintainability and automation within Terraform.

templatefile() allows dynamic generation of files with variables, making it easier to maintain and update configurations compared to manual replacements or external scripts.