GitHub Actions Environment Variables

Environment variables are crucial for passing data between steps and jobs in GitHub Actions workflows. Let’s dive into how to use them effectively.

Default Environment Variables

GitHub Actions provides a set of default environment variables available in every workflow run. Some key ones include:

• GITHUB_REPOSITORY: The owner/repo name
• GITHUB_SHA: The commit SHA that triggered the workflow
• GITHUB_REF: The branch or tag ref that triggered the workflow
• GITHUB_WORKSPACE: The path to the GitHub workspace directory

For a full list, check out the official docs ↗.

Setting Environment Variables

Job-level Variables

Set variables for all steps in a job using the env key:

jobs:
  example-job:
    runs-on: ubuntu-latest
    env:
      MY_VAR: value1
      ANOTHER_VAR: value2
    steps:
      - name: Use job-level vars
        run: echo $MY_VAR $ANOTHER_VAR

Step-level Variables

Set variables for a specific step:

jobs:
  example-job:
    runs-on: ubuntu-latest
    steps:
      - name: Step with custom env
        env:
          STEP_VAR: step_value
        run: echo $STEP_VAR

Adding custom environment variables from a step

To set variables that persist across steps, use the GITHUB_ENV file:

jobs:
  example-job:
    runs-on: ubuntu-latest
    steps:
      - name: Set custom var
        run: echo "CUSTOM_VAR=dynamic_value" >> $GITHUB_ENV
      
      - name: Use custom var
        run: echo $CUSTOM_VAR

Practical Example: Dynamic Configuration

Here’s a workflow that demonstrates various env var techniques:

name: Dynamic Config

on: [push]

jobs:
  configure:
    runs-on: ubuntu-latest
    outputs:
      env_name: ${{ steps.set-env.outputs.env_name }}
    steps:
      - name: Set environment name
        id: set-env
        run: |
          if [[ "${{ github.ref }}" == "refs/heads/main" ]]; then
            echo "ENV_NAME=production" >> $GITHUB_ENV
            echo "env_name=production" >> $GITHUB_OUTPUT
          else
            echo "ENV_NAME=staging" >> $GITHUB_ENV
            echo "env_name=staging" >> $GITHUB_OUTPUT
          fi
      - name: Display env from previous step
        run: |
          echo "ENV_NAME from previous step: $ENV_NAME"

  deploy:
    needs: configure
    runs-on: ubuntu-latest
    env:
      DEPLOY_ENV: ${{ needs.configure.outputs.env_name }}
    steps:
      - name: Deploy to environment
        run: |
          echo "Deploying to $DEPLOY_ENV"

This workflow:

1. Sets an environment name based on the branch
2. Passes the env name to a subsequent job
3. Uses both job-level and step-level environment variables