Persist output

See more info the GH Actions Set up Go section of my Code Cookbooks.

Using GitHub env file

From Environment Variables in the docs.

You can also use the GITHUB_ENV environment file to set an environment variable that the following steps in a workflow can use.

The environment file can be used directly by an action or as a shell command in a workflow file using the run keyword.

That links to Setting an environment variable

echo "{name}={value}" >> $GITHUB_ENV

Creates or updates an environment variable for any actions running next in a job. The action that creates or updates the environment variable does not have access to the new value, but all subsequent actions in a job will have access. Environment variables are case-sensitive and you can include punctuation.

steps:
  - name: Set the value
    id: step_one
    run: echo "action_state=yellow" >> $GITHUB_ENV

  - name: Use the value
    id: step_two
    run: echo "${{ env.action_state }}" # This will output 'yellow'

Examples

Get a version from a file and use it as a parameter for an action in another step.

steps:
  - name: Get Go version
    run: echo "GO_VERSION=$(grep ...)" >> $GITHUB_ENV

  - uses: actions/setup-go@v2
    with:
      go-version: ${{ env.GO_VERSION }}

Use step variable output

Syntax

Note that set-output and save-state are deprecated - see post.

- name: Set output
  run: echo "{name}={value}" >> $GITHUB_OUTPUT
  # Deprecated  
- name: Set output
  run: echo "::set-output name={name}::{value}"

Plain text:

echo "GREETING=hello" >> $GITHUB_OUTPUT

# Deprecated
echo "::set-output name=GREETING::hello"

Variable:

echo "GREETING=$MY_VAR" >> $GITHUB_OUTPUT

# Deprecated
echo "::set-output name=GREETING::$MY_VAR"

Expression - use a subshell.

echo "GREETING=$(grep ...)" >> $GITHUB_OUTPUT

# Deprecated
echo "::set-output name=my_value::$(grep ...)"

Or in two steps:

MY_VAR="$(grep ...)"
echo "name=my_value::$MY_VAR" >> $GITHUB_OUTPUT

Reuse across steps. My trimmed down example from the docs example.

steps:
  - id: step1
    run: echo "name=hello" >> $GITHUB_OUTPUT

  - id: step2
    run: echo "name=test::world" >> $GITHUB_OUTPUT

  - name: Display
    run: |
      echo "Step 1 test: ${{ steps.step1.outputs.test }}"
      echo "Step 2 test: ${{ steps.step1.outputs.test }}"

Don’t forget to set and use the id attributes. If you only have one step with variables set, that typically has the id of vars. See below.

Examples

Get output from npm outdated command, if any.

Note using of single quotes to handle multi-line output.

steps:
 - name: Check for outdated packages
   id: vars
   run: |
     OUTDATED=$(npm outdated) || true
     
     echo "OUTDATED='$OUTDATED'" >> $GITHUB_OUTPUT
      
 - name: Upgrade
   if: ${{ steps.vars.outputs.OUTDATED != '' }}
   run: npm upgrade

Get Go version from go.mod, using set-output method.

steps:
  - name: Get Go version
    id: vars
    run: |
      echo "::set-output name=go_version::$(grep '^go' go.mod | egrep -o '(\d\.\d+)')"
      echo "Using Go version ${{ steps.vars.outputs.go_version }}"

  - name: Set up go
    uses: actions/setup-go@v2
    with:
      go-version: ${{ steps.vars.outputs.go_version }}

Handle Yarn cache directory path. We run yarn cache dir command and store and retrieve the value. From Yarn guide.

steps:
  - name: Get yarn cache
    id: yarn-cache
    run: echo "::set-output name=dir::$(yarn cache dir)"

  - uses: actions/cache@v1
    with:
      path: ${{ steps.yarn-cache.outputs.dir }}
      key: ${{ runner.os }}-yarn-${{ hashFiles('**/yarn.lock') }}
      restore-keys: |
        ${{ runner.os }}-yarn-

Pass between jobs

From docs.

A map of outputs for a job. Job outputs are available to all downstream jobs that depend on this job.

Outputs containing secrets are redacted on the runner and not sent to GitHub Actions.

Syntax

This docs example shows how to reuse values across steps and across jobs. You only need to set up the outputs section for reuse across jobs.

• main.yml

    jobs:
      job1:
        runs-on: ubuntu-latest
  
        outputs:
          output1: ${{ steps.step1.outputs.test }}
          output2: ${{ steps.step2.outputs.test }}
  
        steps:
          - id: step1
            run: echo "::set-output name=test::hello"
  
          - id: step2
            run: echo "::set-output name=test::world"
  
          - name: Display
            run: echo "${{ steps.step1.outputs.test }}"
  
      job2:
        runs-on: ubuntu-latest
        needs: job1
        steps:
          - run: echo ${{ needs.job1.outputs.output1 }} ${{ needs.job1.outputs.output2 }}
  

Returning a JSON object - from docs.

• main.yml

    jobs:
      job1:
        runs-on: ubuntu-latest
  
        outputs:
          matrix: ${{ steps.set-matrix.outputs.matrix }}
  
        steps:
          - id: set-matrix
            run: echo '::set-output name=matrix::{"include":[{"project":"foo","config":"Debug"},{"project":"bar","config":"Release"}]}'
  
      job2:
        needs: job1
  
        runs-on: ubuntu-latest
  
        strategy:
          matrix: ${{ fromJSON(needs.job1.outputs.matrix) }}
  
        steps:
          - run: build