Difference between 'run:' and 'run: |' in GitHub Actions

Question

What is the difference between run: and run: | in GitHub Actions?

The context can be found here

name: Create Docker Container

on: [push]

jobs:
  mlops-container:
    runs-on: ubuntu-latest
    defaults:
      run:
        working-directory: ./week_7_ecr
    steps:
      - name: Checkout
        uses: actions/checkout@v2
        with:
          ref: ${{ github.ref }}
      - name: Configure AWS Credentials
        uses: aws-actions/configure-aws-credentials@v1
        with:
          aws-access-key-id: ${{ secrets.AWS_ACCESS_KEY_ID }}
          aws-secret-access-key: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
          aws-region: us-west-2
      - name: Build container
        run: |
          docker build --build-arg AWS_ACCOUNT_ID=${{ secrets.AWS_ACCOUNT_ID }} \
                       --build-arg AWS_ACCESS_KEY_ID=${{ secrets.AWS_ACCESS_KEY_ID }} \
                       --build-arg AWS_SECRET_ACCESS_KEY=${{ secrets.AWS_SECRET_ACCESS_KEY }} \
                       --tag mlops-basics .
      - name: Push2ECR
        id: ecr
        uses: jwalton/gh-ecr-push@v1
        with:
          access-key-id: ${{ secrets.AWS_ACCESS_KEY_ID }}
          secret-access-key: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
          region: us-west-2
          image: mlops-basics:latest

Answer 1

"|" allows you to execute multiline commands under a single step in a job.

There are some advantages and disadvantages of doing that. Running a command that contains multiple lines can make it harder to identify the problem and you will have to check logs to identify the problem. When you split all commands into steps, you will see much faster which has failed from a top of workflow failure.