resource output value from one plan into another plan - terraform

Question

I have two plans, in which I am creating two different servers(just for example otherwise it's really complex). In one plan, I am outputing the value of the security group like this:
output "security_group_id" {
value = "${aws_security_group.security_group.id}"
}
I have second plan, in which I want to use that value, how I can achieve it, I have tried couple of things but nothing work for me.
I know how to use the output value return by module but don't know that how I can use the output of one plan to another.

Answer 1

When an output is used in the top-level module of a configuration (the directory where you run terraform plan) its value is recorded in the Terraform state.
In order to use this value from another configuration, the state must be published to a location where it can be read by the other configuration. The usual way to achieve this is to use Remote State.
With remote state enabled for the first configuration, it becomes possible to read the resulting values from the second configuration using the terraform_remote_state data source.
For example, it's possible to keep the state for the first configuration in Amazon S3 by using a backend configuration like the following:
terraform {
backend "s3" {
bucket = "example-s3-bucket"
key = "example-bucket-key"
region = "us-east-1"
}
}
After adding this to the first configuration, Terraform will prompt you to run terraform init to initialize the new backend, which includes migrating the existing state to be stored on S3.
Then in the second configuration this can be retrieved by providing the same configuration to the terraform_remote_state data source:
data "terraform_remote_state" "example" {
backend = "s3"
config {
bucket = "example-s3-bucket"
key = "example-bucket-key"
region = "us-east-1"
}
}
resource "aws_instance" "foo" {
# ...
vpc_security_group_ids = "${data.terraform_remote_state.example.security_group_id}"
}
Note that since the second configuration is reading the state from the first it is necessary to terraform apply the first configuration so that this value will actually be recorded in the state. The second config must be re-applied any time the outputs are changed in the first.

Answer 2

For the local backend the process is same. In first step, we need to declare the following code snippet to publish the state.
terraform {
backend local {
path = "./terraform.tfstate"
}
}
When you execute terraform init and terraform apply command, please observe that in .terraform directory new terraform.tfsate file would be created which contains backend information and tell terraform to use the following tfstate file.
Now in the second configuration we need to use data source to import the outputs by using this code snippet
data "terraform_remote_state" "test" {
backend = "local"
config {
path = "${path.module}/../regionalvpc/terraform.tfstate"
}
}