How to use input variables and output variables with Terraform?

In Terraform, input variables and output variables are used to make the configuration more flexible and reusable.

Input Variables:

• They allow you to pass values into your Terraform configuration from outside.
• Defined using the variable block in the Terraform configuration file.
• Can be used to parameterize configurations, making them applicable to different environments or scenarios.

Example of defining an input variable:

variable "instance_type" {
  description = "The type of instance to create"
  type        = string
}

You can then use this variable in your resource definitions:

resource "aws_instance" "example" {
  ami           = "ami-12345678"
  instance_type = var.instance_type
}

When running Terraform, you can provide a value for this variable using the -var option:

terraform apply -var="instance_type=t2.micro"

Output Variables:

• They allow you to export values from your Terraform configuration to be used elsewhere.
• Defined using the output block in the Terraform configuration file.
• Useful for sharing information generated by Terraform with other systems or for verification.

Example of defining an output variable:

output "instance_public_ip" {
  description = "The public IP address of the instance"
  value       = aws_instance.example.public_ip
}

After running terraform apply, Terraform will display the value of this output variable.

Relation to Cloud Services:
When using Terraform with cloud services, such as those offered by Tencent Cloud, input variables can be used to specify parameters like region, instance type, or network settings specific to your needs. Output variables can then provide details like the public IP of the created instance, which might be necessary for further configuration or access.

For example, if you are using Tencent Cloud's CVM (Cloud Virtual Machine) service with Terraform, you might define input variables for the CVM instance type and region, and output variables for the instance ID and public IP.

This approach enhances the portability and maintainability of your infrastructure as code, allowing you to easily adapt to changes in your environment or requirements.