Git & GitHub Interview Question #109

What are expressions and contexts in GitHub Actions?

Advanced GitHub Actions, Repository Internals, Submodules, LFS & Diagnostic Tools Senior Advanced

Quick Interview Answer

Expressions use the ${{ ... }} syntax to evaluate workflow data. Contexts expose structured information about the workflow run, repository, event, matrix, jobs, steps, variables, secrets, and other supported values.

Detailed Explanation

Expressions can control conditions, inputs, environment values, or dynamic configuration. Sensitive values should not be exposed through logging or untrusted expressions.

Code Example

steps:
  - name: Run only on main
    if: ${{ github.ref == 'refs/heads/main' }}
    run: echo "Running on main"

  - run: echo "Repository: ${{ github.repository }}"