Comments in HCL in Terraform - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a single-line comment in HCL.

Terraform

#[1] This is a comment

Drag options to blanks, or click blank then click option'

A This is a comment

Attempts:

3 left

💡 Hint

Common Mistakes

Using // instead of # for single-line comments

Not adding a space after the comment symbol

In HCL, a single-line comment starts with the # symbol followed by the comment text.

2fill in blank

medium

Complete the code to add a multi-line comment in HCL.

Terraform

/*[1]*/

Drag options to blanks, or click blank then click option'

A This is a multi-line comment spanning multiple lines

B This is a single-line comment

C This is not a comment

D This is a wrong comment style

Attempts:

3 left

💡 Hint

Common Mistakes

Using # for multi-line comments

Not closing the multi-line comment properly

Multi-line comments in HCL are enclosed between /* and */. You can write multiple lines inside.

3fill in blank

hard

Fix the error in the comment syntax below by completing the blank.

Terraform

resource "aws_instance" "example" { [1] This resource creates an EC2 instance
  ami           = "ami-123456"
  instance_type = "t2.micro"
}

Drag options to blanks, or click blank then click option'

A//

B--

C/*

D#

Attempts:

3 left

💡 Hint

Common Mistakes

Using // instead of # inside resource blocks

Using SQL style comments like --

In HCL, single-line comments inside blocks use #. Using // or others causes errors.

4fill in blank

hard

Fill both blanks to correctly comment out the variable declaration in HCL.

Terraform

[1] variable "region" { 
  type    = string
  default = "us-west-2"
} [2]

Drag options to blanks, or click blank then click option'

A/*

B#

C*/

D//

Attempts:

3 left

💡 Hint

Common Mistakes

Using # at the end of the block

Using // instead of /* and */ for multi-line comments

To comment out multiple lines in HCL, use /* to start and */ to end the comment block.

5fill in blank

hard

Fill all three blanks to add a comment inside a resource block and a multi-line comment outside.

Terraform

/*[1]*/
resource "aws_s3_bucket" "bucket" {
  [2] Bucket for storing logs
  bucket = "my-log-bucket"
  acl    = "private"
}
[3]

Drag options to blanks, or click blank then click option'

A This is a multi-line comment spanning lines

B#

C/*

D*/

Attempts:

3 left

💡 Hint

Common Mistakes

Using # for multi-line comments outside resource blocks

Using /* inside resource blocks for single-line comments

The multi-line comment outside the resource uses /* and */. Inside the resource, use # for single-line comments.

Practice

1. What is the purpose of comments in Terraform's HCL language?

easy

A. To explain the code without affecting its execution

B. To execute additional commands

C. To speed up the Terraform apply process

D. To delete unused resources automatically

Solution

1. Step 1: Understand the role of comments

   Comments are notes in code that help explain what the code does but do not change how it runs.

2. Step 2: Identify the correct purpose

   Since comments do not execute or affect resources, their purpose is purely explanatory.

3. Final Answer:

   To explain the code without affecting its execution -> Option A

4. Quick Check:

   Comments explain code [OK]

Hint: Comments never change code behavior, only explain it [OK]

Common Mistakes:

• Thinking comments run code
• Assuming comments speed up deployment
• Believing comments delete resources

2. Which of the following is a valid single-line comment syntax in Terraform HCL?

easy

A. /* This is a comment */

B. # This is a comment

C. -- This is a comment

D. %% This is a comment

Solution

1. Step 1: Recall single-line comment syntax in HCL

   Terraform HCL supports # and // for single-line comments.

2. Step 2: Match options with valid syntax

   # This is a comment uses #, which is valid. /* This is a comment */ is multi-line comment syntax. Options C and D are invalid in HCL.

3. Final Answer:

   # This is a comment -> Option B

4. Quick Check:

   Single-line comment = # or // [OK]

Hint: Single-line comments start with # or // only [OK]

Common Mistakes:

• Using -- or %% which are not valid in HCL
• Confusing multi-line comment syntax for single-line
• Omitting comment symbols

3. What will happen if you run this Terraform code snippet?

resource "aws_instance" "example" {
  ami           = "ami-123456"
  instance_type = "t2.micro"  # This is a small instance
  // This line is ignored
  /* multi-line
     comment here */
}

medium

A. Terraform will create an AWS instance ignoring all comments

B. Terraform will throw a syntax error due to comments

C. Terraform will create an instance but ignore the instance_type

D. Terraform will skip the resource block entirely

Solution

1. Step 1: Understand how comments affect Terraform code

   Comments are ignored by Terraform during execution and do not affect resource creation.

2. Step 2: Analyze the code snippet

   The resource block is valid with comments in single-line (#, //) and multi-line (/* */) forms. Terraform will create the instance as specified.

3. Final Answer:

   Terraform will create an AWS instance ignoring all comments -> Option A

4. Quick Check:

   Comments ignored, resource created [OK]

Hint: Comments do not affect resource creation or syntax [OK]

Common Mistakes:

• Thinking comments cause syntax errors
• Assuming comments disable resource properties
• Believing comments skip resource blocks

4. Identify the error in this Terraform snippet:

resource "aws_s3_bucket" "bucket" {
  bucket = "my-bucket"
  /* This is a multi-line comment
  missing the closing tag

medium

A. Single-line comment used incorrectly

B. Incorrect resource type name

C. Bucket name must be numeric

D. Missing closing */ for multi-line comment

Solution

1. Step 1: Check multi-line comment syntax

   Multi-line comments start with /* and must end with */. The snippet lacks the closing */.

2. Step 2: Confirm other parts are correct

   Resource type and bucket name are valid. No single-line comment issues.

3. Final Answer:

   Missing closing */ for multi-line comment -> Option D

4. Quick Check:

   Unclosed multi-line comment [OK]

Hint: Always close multi-line comments with */ [OK]

Common Mistakes:

• Forgetting to close multi-line comments
• Confusing resource type errors with comment errors
• Assuming bucket names must be numeric

5. You want to temporarily disable a block of Terraform code without deleting it. Which comment style should you use to comment out multiple lines safely?

hard

A. Use # at the start of each line

B. Use // at the start of each line

C. Use /* */ to wrap the entire block

D. Use XML style <!-- --> comments

Solution

1. Step 1: Review comment styles for multiple lines

   Single-line comments (# or //) require prefixing each line, which is tedious for many lines.

2. Step 2: Identify the best multi-line comment method

   Using /* */ wraps multiple lines easily, disabling the entire block at once.

3. Step 3: Exclude invalid options

   XML style comments are not valid in HCL.

4. Final Answer:

   Use /* */ to wrap the entire block -> Option C

5. Quick Check:

   Multi-line comments use /* */ [OK]

Hint: Wrap multiple lines with /* and */ to comment out block [OK]

Common Mistakes:

• Using # or // for many lines instead of block comment
• Trying XML style comments which are invalid
• Not closing multi-line comment properly