How do I get the output of a specific step in GitHub Actions?

Question

I have this GitHub Actions workflow which runs tests, but now I am integrating slack notification in it. I want to get the output of the Run tests step and send it as a message in the slack step.

  - name: Run tests
    run: |
      mix compile --warnings-as-errors
      mix format --check-formatted
      mix ecto.create
      mix ecto.migrate
      mix test
    env:
      MIX_ENV: test
      PGHOST: localhost
      PGUSER: postgres

  - name: Slack Notification
    uses: rtCamp/action-slack-notify@master
    env:
      SLACK_MESSAGE: Run tests output
      SLACK_TITLE: CI Test Suite
      SLACK_WEBHOOK: ${{ secrets.SLACK_WEBHOOK }}

Answer 1

You need to do 3 things:

1. Add an id to the step you want the output from
2. Create the outputs using the set-output command
3. Use the id and the output name in another step to get the outputs and then join them into one message for slack

- name: Run tests
  run: |
    echo "::set-output name=mix-compile--warnings-as-errors::$(mix compile --warnings-as-errors)\n"
    echo "::set-output name=mix-format--check-formatted::$(mix format --check-formatted)\n"
    echo "::set-output name=mix-ecto_create::$(mix ecto.create)\n"
    echo "::set-output name=mix-ecto_migrate::$(mix ecto.migrate)\n"
    echo "::set-output name=mix-test::$(mix test)\n"
  id: run_tests
  env:
    MIX_ENV: test
    PGHOST: localhost
    PGUSER: postgres

- name: Slack Notification
  uses: rtCamp/action-slack-notify@v2
  env:
    SLACK_MESSAGE: ${{join(steps.run_tests.outputs.*, '\n')}}
    SLACK_TITLE: CI Test Suite
    SLACK_WEBHOOK: ${{ secrets.SLACK_WEBHOOK }}

See Metadata Syntax for outputs name description

Answer 2

The problem with the current accepted answer is that the result for the step will always be success since the test execution result is being masked by the echo command.

This modification to the last line should work in preserving the original exit status:

mix test 2>&1 | tee test.log
result_code=${PIPESTATUS[0]}
echo "::set-output name=mix-test::$(cat test.log)"
exit $result_code

Answer 3

I just wanted to add @smac89's solution was helpful but didn't quite work for me. I'm using a different Slack action (pullreminders/slack-action) to build more specific content. I found that I was getting single-quotes where each newline was, and my leading spaces on each line were also being truncated. After reading https://github.com/actions/toolkit/issues/403 and playing around, I found that in my case, I needed newlines to actually be escaped in the output (a literal \n), so I replaced \n characters with \\n. Then, I replaced regular space characters with a Unicode 'En Space' character.

Here's what worked:

Bash Run Step:

        Tools/get-changed-fields.sh src/objects origin/${{ env.DIFF_BRANCH }} > changed-fields.out
        output="$(cat changed-fields.out)"
        output="${output//$'\n'/\\n}"
        output="${output// /?}"     # replace regular space with 'En Space'
        echo "::set-output name=changed-fields-output::$output"

Slack Notification Step:

    - name: Changed Fields Slack Notification
      if: ${{ success() && steps.summarize-changed-fields.outputs.changed-fields-output != '' && steps.changed-fields-cache.outputs.cache-hit != 'true' }}
      env:
        SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}
      uses: pullreminders/slack-action@master
      with:
        args: '{\"channel\":\"${{ env.SUCCESS_SLACK_CHANNEL }}\",\"attachments\":[{\"color\":\"#36a64f\",\"title\":\"Changed Fields Report:\",\"author_name\":\"${{ github.workflow }} #${{ github.run_number }}: ${{ env.BRANCH }} -> ${{ env.TARGET_ORG }} (by: ${{ github.actor }})\",\"author_link\":\"${{ github.server_url }}/${{ github.repository }}/runs/${{ github.run_id }}\",\"text\":\"```\n${{ steps.summarize-changed-fields.outputs.changed-fields-output }}\n```\"}]}'

Answer 4

I made an action with the same interface as run that stores stdout and stderr in output variables to maybe simplify some cases like this:

- name: Run tests
  uses: mathiasvr/command-output@v1
  id: tests
  with:
    run: |
      mix compile --warnings-as-errors
      mix format --check-formatted
      mix ecto.create
      mix ecto.migrate
      mix test

- name: Slack Notification
  uses: rtCamp/action-slack-notify@master
  env:
    SLACK_MESSAGE: ${{ steps.tests.outputs.stdout }}         
    SLACK_TITLE: CI Test Suite
    SLACK_WEBHOOK: ${{ secrets.SLACK_WEBHOOK }}