9. Terraform Variables

Input Variables

We can define input variables in the config file as follows

variable "subnet_prefix" {
  description = "cidr block for the subnet"
  default = "10.0.2.0/24"
  type = string
}

• Accessed as var.<name>

• default value like name suggests is the default value when we don't assign any value to it

• type = any means any data type is accepted

  • We can also use lists type or list of objects

Usage

Order of precedence // lowest -> highest

1. If we dont specify any value, it will ask us for input while running terraform apply.

2. Second is the default value in declaration block

3. TF_VAR_<name> environment variable

4. Best way is to use a seperate file for variables with name terraform.tfvars

   • We can assign values in that file like

   • subnet_prefix = "10.0.1.0/24"
     avail_zone = "eu-west-1"

   • If you want to use other file like example.tfvars, you have to specify it while applying config like terraform apply -var-file example.tfvars

5. *.auto.tfvars file

6. Command line arguments to enter the value of the variables like terraform apply -var "subnet_prefix=10.0.1.0/24" or -var-file

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Local Variables

We can define local variables in the config file as follows

locals {
  service_name = "My Service"
  owner = "NomanAziz"
}

• Can be accessed as local.<name>

• Temporary variables within the scope of the function

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Output Variables

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Types

Primitive Types

1. string

2. number

3. bool

Complex Types

1. list(<TYPE>)

2. set(<TYPE>)

3. map(<TYPE>)

4. object({ <ATTR NAME> = <TYPE>, ... })

5. tuple([<TYPE>, ...])

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Sensitive Data

Mark variables as sensitive

sensitive=true

Pass to terraform apply with

• TV_VAR_variable

• -var (retrieved from secret manager at runtime)

Can also use external secret store

• AWS Secrets manager

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