Splat expressions in Terraform - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to get all instance IDs from the aws_instance resource.

Terraform

output "instance_ids" {
  value = aws_instance.example[1].id
}

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

A[*]

B.*

C[.]

D[+]

Attempts:

3 left

💡 Hint

Common Mistakes

Using dot (.) instead of [*] for splat expression

Using incorrect brackets like [.] or [+]

The splat expression aws_instance.example[*].id collects the id attribute from all instances in the resource list.

2fill in blank

medium

Complete the code to get all private IP addresses from multiple aws_instance resources.

Terraform

output "private_ips" {
  value = aws_instance.web[1].private_ip
}

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

A.*

B[*]

C[]

D[.]

Attempts:

3 left

💡 Hint

Common Mistakes

Using dot-star (.*) which is invalid in Terraform

Using empty brackets [] without asterisk

The splat expression aws_instance.web[*].private_ip returns a list of private IPs from all instances named 'web'.

3fill in blank

hard

Fix the error in the splat expression to correctly get all subnet IDs.

Terraform

output "subnet_ids" {
  value = aws_subnet.example[1].id
}

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

A[*]

B.*

C.[]

D[.]

Attempts:

3 left

💡 Hint

Common Mistakes

Using dot-star (.*) which is not valid in Terraform

Using dot with brackets like .[] or [.]

The correct splat expression uses [*] to get all IDs from the aws_subnet resource list.

4fill in blank

hard

Fill both blanks to create a list of all security group names from aws_security_group resources.

Terraform

output "sg_names" {
  value = aws_security_group.[1][2].name
}

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

Aweb

Bdb

C[*]

D.*

Attempts:

3 left

💡 Hint

Common Mistakes

Using dot-star (.*) instead of [*]

Using wrong resource name like db instead of web

Use the resource name web and the splat operator [*] to get all security group names.

5fill in blank

hard

Fill all three blanks to output a list of all tags 'Name' values from aws_instance resources.

Terraform

output "instance_names" {
  value = aws_instance.[1][2].tags[3]
}

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

Aapp

B[*]

C["Name"]

D.*

Attempts:

3 left

💡 Hint

Common Mistakes

Using dot-star (.*) instead of [*]

Accessing tags.Name instead of tags["Name"]

Using wrong resource name like web instead of app

Use the resource name app, the splat operator [*], and access the tag ["Name"] to get all instance names.

Practice

1.

What does a splat expression in Terraform do?

Example: aws_instance.example[*].id

easy

A. Collects the id attribute from all aws_instance.example resources into a list

B. Creates a new resource named id for each instance

C. Deletes all aws_instance.example resources

D. Filters instances with id equal to example

Solution

1. Step 1: Understand the splat operator *

   The * means 'all items' in the list of resources.

2. Step 2: Collect attribute values

   The expression aws_instance.example[*].id collects the id attribute from every instance in aws_instance.example.

3. Final Answer:

   Collects the id attribute from all aws_instance.example resources into a list -> Option A

4. Quick Check:

   Splat expression collects attributes [OK]

Hint: Remember: * means all items, collect their attributes [OK]

Common Mistakes:

• Thinking splat creates or deletes resources
• Confusing splat with filtering
• Assuming splat returns a single value

2.

Which of the following is the correct syntax for a splat expression to get all name attributes from a resource list aws_s3_bucket.buckets?

easy

A. aws_s3_bucket.buckets[*].name

B. aws_s3_bucket.buckets.name[*]

C. aws_s3_bucket.buckets[].name

D. aws_s3_bucket.buckets.name

Solution

1. Step 1: Identify splat operator position

   The splat operator * must come immediately after the resource list name inside square brackets.

2. Step 2: Confirm attribute access

   The correct syntax is resource_list[*].attribute, so aws_s3_bucket.buckets[*].name is correct.

3. Final Answer:

   aws_s3_bucket.buckets[*].name -> Option A

4. Quick Check:

   Splat syntax = resource_list[*].attribute [OK]

Hint: Put * inside brackets right after resource list name [OK]

Common Mistakes:

• Placing * after attribute name
• Using [] without * inside
• Omitting brackets for splat

3.

Given the Terraform code snippet:

resource "aws_instance" "web" {
  count = 3
  ami           = "ami-123456"
  instance_type = "t2.micro"
}

output "instance_ids" {
  value = aws_instance.web[*].id
}

What will be the output of instance_ids after deployment?

medium

A. A list of 0 elements because no instances are created

B. A list of 3 instance IDs, one for each created instance

C. An error because splat cannot be used with count

D. A single instance ID of the first instance

Solution

1. Step 1: Understand resource count creates multiple instances

   The count = 3 creates 3 instances named aws_instance.web[0], aws_instance.web[1], and aws_instance.web[2].

2. Step 2: Splat expression collects all instance IDs

   The expression aws_instance.web[*].id collects the id attribute from all 3 instances into a list.

3. Final Answer:

   A list of 3 instance IDs, one for each created instance -> Option B

4. Quick Check:

   count 3 + splat = list of 3 IDs [OK]

Hint: count creates multiple; splat collects all attributes [OK]

Common Mistakes:

• Thinking splat fails with count
• Expecting single ID instead of list
• Assuming no instances created

4.

Identify the error in this Terraform snippet using splat expressions:

output "bucket_names" {
  value = aws_s3_bucket.buckets.name[*]
}

medium

A. Output blocks cannot use splat expressions

B. The resource name aws_s3_bucket.buckets is invalid

C. Missing quotes around the attribute name

D. The splat operator * is incorrectly placed after the attribute name

Solution

1. Step 1: Check splat operator position

   The splat operator * must be inside brackets immediately after the resource list, not after the attribute.

2. Step 2: Correct syntax

   The correct syntax is aws_s3_bucket.buckets[*].name, not aws_s3_bucket.buckets.name[*].

3. Final Answer:

   The splat operator * is incorrectly placed after the attribute name -> Option D

4. Quick Check:

   Splat must be after resource list, not attribute [OK]

Hint: Put * right after resource list in brackets, not after attribute [OK]

Common Mistakes:

• Placing * after attribute name
• Confusing resource and attribute order
• Thinking output blocks disallow splat

5.

You have a list of AWS EC2 instances created with count = 4. You want to output a list of their public IPs but only for instances that have a tag Environment set to production. Which Terraform expression correctly uses splat and filtering?

hard

A. aws_instance.web[*].public_ip

B. aws_instance.web[*].tags.Environment == "production" ? aws_instance.web[*].public_ip : []

C. [for i in aws_instance.web : i.public_ip if i.tags.Environment == "production"]

D. aws_instance.web[?tags.Environment=="production"].public_ip

Solution

1. Step 1: Understand splat collects all attributes without filtering

   The expression aws_instance.web[*].public_ip collects all public IPs, no filtering.

2. Step 2: Use for-expression with condition for filtering

   The correct way to filter is using a for-expression with an if condition: [for i in aws_instance.web : i.public_ip if i.tags.Environment == "production"].

3. Final Answer:

   [for i in aws_instance.web : i.public_ip if i.tags.Environment == "production"] -> Option C

4. Quick Check:

   Filter with for-expression + if, not splat alone [OK]

Hint: Use for-expression with if to filter, splat alone can't filter [OK]

Common Mistakes:

• Using splat without filtering
• Trying to filter inside splat syntax
• Using invalid filter syntax