Infrastructure as Code Using Terraform/

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Working with Outputs in Terraform

Working with Outputs in Terraform

Learn how to work with outputs in Terraform configuration.

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Overview

Previously, we looked at the flexibility that using variables, especially input variables, gives us. When we create resources in Terraform, these resources have unique attributes that can be passed on as output to create another resource. The syntax for creating an output variable is as below:

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output "variable_name" {
  decsription = "Any description"
  value = "${resource_type.resource_name.attribute}"
}

A practical use case

Let’s consider a situation where we have to create an EC2 instance and then obtain the public IP address so that we can initiate an SSH connection to the instance. We can create the needed resource and then use the output keyword to obtain the public IP address, as shown below:

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resource "aws_vpc" "my_vpc" {
  cidr_block = "10.0.0.0/16"
}
resource "aws_internet_gateway" "igw" {
  vpc_id = aws_vpc.my_vpc.id
}
resource "aws_route_table" "public" {
  vpc_id = aws_vpc.my_vpc.id
  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_internet_gateway.igw.id
  }
}
resource "aws_default_route_table" "default" {
  default_route_table_id = aws_vpc.my_vpc.default_route_table_id
  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_internet_gateway.igw.id
  }
}
resource "aws_subnet" "demo_subnet" {
  vpc_id     = aws_vpc.my_vpc.id
  cidr_block = "10.0.1.0/24"
}
resource "aws_security_group" "http_access" {
 name        = "http_access"
 description = "Allow HTTP inbound traffic"
 vpc_id      = aws_vpc.my_vpc.id
 
 ingress {
   description = "HTTP Access"
   from_port   = 80
   to_port     = 80
   protocol    = "tcp"
   cidr_blocks = ["0.0.0.0/0"]
 }
 
 ingress {
   description = "SSH Access"
   from_port   = 22
   to_port     = 22
   protocol    = "tcp"
   cidr_blocks = ["0.0.0.0/0"]
 }
  egress {
   from_port   = 0
   to_port     = 0
   protocol    = "-1"
   cidr_blocks = ["0.0.0.0/0"]
 }
 
 tags = {
   Name = "http_access"
 }
}
resource "aws_eip" "my_eip" {
  vpc = true
}
resource "aws_instance" "demo_instance" {
  ami           = "ami-0a606d8395a538502"
  instance_type = "t2.micro"
  key_name      = "sampleKey"
  subnet_id     = aws_subnet.demo_subnet.id
  vpc_security_group_ids = [aws_security_group.http_access.id]
  associate_public_ip_address = true
  tags = {
    Name = "new-instance" 
  }
}
output "my_instance2_ip" {
  value = aws_instance.demo_instance.public_ip
}

Terraform outputs are available after a resource is created using terraform apply. The ...