Variables

Variable types

• string

• number

• bool (true/false)

• list(datatype)

• map(datatype)

• set(datatype)

Input Variables

• Terraform variables allow you to write configuration that is flexible and easier to re-use.

• Example to declare a variable in variables file say variables.tf:

  variable "instance_name" {
  description = "Value of the Name tag for the EC2 instance"
  type        = string
  default     = "ExampleAppServerInstance"
  }
  
  # In .tf configuration file where u need to use the variable make changes using `var.variable_name`
  
  resource "aws_instance" "app_server" {
      ami = "ami-08d70e59c07c61a3a"
      instance_type = "t2.micro"
      tags = {
          Name = var.instance_name
      }
  }

Note: Terraform loads all files in the current directory ending in .tf, so you can name your configuration files however you choose.

• To override the default value of a variable use -var flag.

$ terraform apply -var "instance_name=anotherName"

• Setting variables via the command-line will not save their values. Terraform supports many ways to use and set variables so you can avoid having to enter them repeatedly as you execute commands.

• If you do not set a default value for a variable, you must assign a value before Terraform can apply the configuration. Terraform does not support unassigned variables.

• You can also store variable values in a file terraform.tfvars which is the default file that terrafom looks for when applying configuration, or explicit file location can also be passed using -var-file file_name.tfvars.

• To learn more, follow here.

Output Variables

• Create a file called outputs.tf in your terraform directory (i.e in the directory in which your terraform file resides).

    output "instance_id" {
        description = "ID of the EC2 instance"
        value = aws_instance.app_server.id
    }

    output "instance_public_ip" {
        description = "Public IP address of the EC2 instance"
        value = aws_instance.app_server.public_ip
    }

• Refer the command list for how to query the output variable.

• To learn more about output variables visit here.