I want to identify the public ip of the terraform execution environment and add it to the security group

There’s an easier way to do that without any scripts. The trick is having a website such as icanhazip.com which retrieve your IP, so set it in your terraform file as data:

data "http" "myip" {
  url = "http://ipv4.icanhazip.com"
}

And whenever you want to place your IP just use data.http.myip.body, example:

ingress {
  from_port = 5432
  to_port = 5432
  protocol = "tcp"
  cidr_blocks = ["${chomp(data.http.myip.body)}/32"]
}

• Note I used terraform chomp() method to remove any trailing space or new line which comes with body.

• You can use your ipv6 with http://ipv6.icanhazip.com. Take care by just using http://icanhazip.com because it can retrieve ipv4 or ipv6