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GitHub Actions Output Format

· 2 min read
Erik Osterman
Erik Osterman
Founder @ Cloud Posse

Atmos now supports a dedicated github output format for atmos terraform output, making it easier than ever to pass Terraform outputs between GitHub Actions steps.

What's New​

The new --format=github option for atmos terraform output automatically writes outputs to $GITHUB_OUTPUT in the format GitHub Actions expects, including proper handling of multiline values using heredoc syntax.

# In a GitHub Actions workflow
atmos terraform output vpc -s dev --format=github

This writes outputs directly to $GITHUB_OUTPUT, making them available to subsequent workflow steps.

Why This Matters​

Previously, passing Terraform outputs between GitHub Actions steps required manual formatting or shell scripting to handle:

  • Multiline values (JSON objects, lists, multi-line strings)
  • Special characters that need escaping
  • The correct $GITHUB_OUTPUT file format

The github format handles all of this automatically:

  • Single-line values are written as key=value
  • Multiline values use heredoc syntax: key<<DELIMITER\nvalue\nDELIMITER
  • Complex types (maps, arrays) are JSON-encoded for easy parsing

Example Workflow​

jobs:
  deploy:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v4

      - name: Get Terraform Outputs
        id: outputs
        run: atmos terraform output vpc -s dev --format=github

      - name: Use Outputs
        run: |
          echo "VPC ID: ${{ steps.outputs.outputs.vpc_id }}"
          echo "Subnets: ${{ steps.outputs.outputs.private_subnet_ids }}"

Usage Options​

Automatic $GITHUB_OUTPUT Detection​

When running in GitHub Actions, the format automatically writes to $GITHUB_OUTPUT:

atmos terraform output vpc -s dev --format=github

Custom Output File​

You can specify a different output file if needed:

atmos terraform output vpc -s dev --format=github --output-file=outputs.txt

Combined with Other Options​

The github format works with other output options:

# Uppercase keys for conventional ENV_VAR naming
atmos terraform output vpc -s dev --format=github --uppercase

# Flatten nested maps
atmos terraform output vpc -s dev --format=github --flatten

# Skip init for faster execution in CI
atmos terraform output vpc -s dev --format=github --skip-init

Output Format Details​

Simple Values​

vpc_id=vpc-12345
region=us-east-1
enabled=true

Multiline Values (Heredoc)​

For values containing newlines, the format uses GitHub's heredoc syntax:

vpc_config<<ATMOS_EOF_vpc_config
{
  "id": "vpc-12345",
  "cidr": "10.0.0.0/16"
}
ATMOS_EOF_vpc_config

Documentation​

For complete documentation on terraform output formatting options, see:

Get Involved​

Try out the new GitHub Actions output format and let us know what you think! File issues or feature requests on GitHub.