Variable:
A variable helps to store data values.
Terraform supports multiple ways to use variables in configuration blocks.
Case1: Default values:
Variable “hello” {
Default = “t2.small”
}
“In above case we are declaring a variable “hello” and the default value is “t2.small” that refers to the instance vaule of the EC2 configuration code as shown below “
resource “aws_instance” “myec” {
ami = “ami-0a0ad6b70e61be944”
instance_type = “t2.large”
}
Case2: Passing multiple values
When we have multiple files we can pass variables through a file we need to store them in a file called “terraform.tfvars”
Example usage:
Variable “insttype” {}
Variable “amiid” {}
The values of the above variables should be stored in variables.tf file
amiid = “ami-0a0ad6b70e61be944”
insttype = “t2.large”
We have declared above variables.if we need to use them in source code the syntax is : VAR.varname
resource “aws_instance” “myec” {
ami = var.insttype
instance_type = var.amiid
}
When we do terraform apply the values will be associated to the code.
Case3:
Passing values through a file:
We can pass multiple variables through a file.the syntax to pass multiple variables through a file is :
Syntax
Terraform plan –var-file= “myfile.tfvars”
Here myfile consists of the variables and their associated values.
Example:
Instype= “t2.small”
amiid = “ami-0a0ad6b70e61be944”
Now to use these values in code
resource “aws_instance” “myec” {
ami = var.insttype
instance_type = var.amiid
}
Case 4:
Using envnvironment variables
Environment variables can be used to set variables. The environment variables must be in the format TF_VAR_name and this will be checked last for a value. For example:
export TF_VAR_region=ap-south -1
export TF_VAR_ami=ami-14dg56
Hope this document is very useful for you in decalring terraform variables
