GitHub Actions example workflow — Outputs 2

09-outputs-2.yml

name: outputs-2
on: workflow_dispatch
jobs:
  my-job:
    runs-on: ubuntu-latest
    steps:
      - name: step-1
        id: xyz
        run: echo "::set-output name=ip-address::$(curl -s ifconfig.me)"
      - name: step-2
        run: echo "${{ steps.xyz.outputs.ip-address }}"

For people finding this: "::set-output" does work within a script; you don't have to put it in the action YAML. (It's possible GitHub has changed something since the comment above saying the opposite, but I just tried it and it worked for me.)