Contexts reference

Available contexts

As part of an expression, you can access context information using one of two syntaxes.

• Index syntax: github['sha']
• Property dereference syntax: github.sha

In order to use property dereference syntax, the property name must start with a letter or _ and contain only alphanumeric characters, -, or _.

If you attempt to dereference a nonexistent property, it will evaluate to an empty string.

Determining when to use contexts

GitHub Actions includes a collection of variables called contexts and a similar collection of variables called default variables. These variables are intended for use at different points in the workflow:

• Default environment variables: These environment variables exist only on the runner that is executing your job. For more information, see Variables reference.
• Contexts: You can use most contexts at any point in your workflow, including when default variables would be unavailable. For example, you can use contexts with expressions to perform initial processing before the job is routed to a runner for execution; this allows you to use a context with the conditional if keyword to determine whether a step should run. Once the job is running, you can also retrieve context variables from the runner that is executing the job, such as runner.os. For details of where you can use various contexts within a workflow, see Context availability.

The following example demonstrates how these different types of variables can be used together in a job:

name: CI
on: push
jobs:
  prod-check:
    if: ${{ github.ref == 'refs/heads/main' }}
    runs-on: ubuntu-latest
    steps:
      - run: echo "Deploying to production server on branch $GITHUB_REF"

name: CI
on: push
jobs:
  prod-check:
    if: ${{ github.ref == 'refs/heads/main' }}
    runs-on: ubuntu-latest
    steps:
      - run: echo "Deploying to production server on branch $GITHUB_REF"

In this example, the if statement checks the github.ref context to determine the current branch name; if the name is refs/heads/main, then the subsequent steps are executed. The if check is processed by GitHub Actions, and the job is only sent to the runner if the result is true. Once the job is sent to the runner, the step is executed and refers to the $GITHUB_REF variable from the runner.

Context availability

Different contexts are available throughout a workflow run. For example, the secrets context may only be used at certain places within a job.

In addition, some functions may only be used in certain places. For example, the hashFiles function is not available everywhere.

The following table lists the restrictions on where each context and special function can be used within a workflow. The listed contexts are only available for the given workflow key, and may not be used anywhere else. Unless listed below, a function can be used anywhere.

Example: printing context information to the log

You can print the contents of contexts to the log for debugging. The toJSON function is required to pretty-print JSON objects to the log.

name: Context testing
on: push

jobs:
  dump_contexts_to_log:
    runs-on: ubuntu-latest
    steps:
      - name: Dump GitHub context
        env:
          GITHUB_CONTEXT: ${{ toJson(github) }}
        run: echo "$GITHUB_CONTEXT"
      - name: Dump job context
        env:
          JOB_CONTEXT: ${{ toJson(job) }}
        run: echo "$JOB_CONTEXT"
      - name: Dump steps context
        env:
          STEPS_CONTEXT: ${{ toJson(steps) }}
        run: echo "$STEPS_CONTEXT"
      - name: Dump runner context
        env:
          RUNNER_CONTEXT: ${{ toJson(runner) }}
        run: echo "$RUNNER_CONTEXT"
      - name: Dump strategy context
        env:
          STRATEGY_CONTEXT: ${{ toJson(strategy) }}
        run: echo "$STRATEGY_CONTEXT"
      - name: Dump matrix context
        env:
          MATRIX_CONTEXT: ${{ toJson(matrix) }}
        run: echo "$MATRIX_CONTEXT"

name: Context testing