terraform-upgrade.sh

#!/usr/bin/env bash

set -e

base_url="https://releases.hashicorp.com/terraform"

latest_version="$(curl --silent "https://releases.hashicorp.com/terraform/" | sed -ne 's/.*<a href="\/terraform\/\(.*\)\/".*/\1/p' | grep -v "rc\|beta" | head -n1)"
current_version="$(terraform -v | sed -ne 's/Terraform v\(.*\)/\1/p')"

if [ "$latest_version" != "$current_version" ]; then
  echo "updating from ${current_version} to ${latest_version}"

  dir="$(mktemp -d --suffix "-terraform-upgrade")"

  pushd "$dir"

  curl --silent -O "${base_url}/${latest_version}/terraform_${latest_version}_SHA256SUMS"
  curl --silent -O "${base_url}/${latest_version}/terraform_${latest_version}_SHA256SUMS.sig"
  curl --silent -O "${base_url}/${latest_version}/terraform_${latest_version}_linux_amd64.zip"

  gpg --verify "terraform_${latest_version}_SHA256SUMS.sig" "terraform_${latest_version}_SHA256SUMS"

  shasum -a 256 -c <(grep "_linux_amd64" "terraform_${latest_version}_SHA256SUMS")

  unzip -o "terraform_${latest_version}_linux_amd64.zip" "terraform" -d ~/bin/

  popd

  rm -r "$dir"
else
  echo "up to date (${latest_version})"
fi