Understanding GitHub Actions

Overview

GitHub Actions help you automate tasks within your software development life cycle. GitHub Actions are event-driven, meaning that you can run a series of commands after a specified event has occurred. For example, every time someone creates a pull request for a repository, you can automatically run a command that executes a software testing script.

This diagram demonstrates how you can use GitHub Actions to automatically run your software testing scripts. An event automatically triggers the workflow, which contains a job. The job then uses steps to control the order in which actions are run. These actions are the commands that automate your software testing.

The components of GitHub Actions

Below is a list of the multiple GitHub Actions components that work together to run jobs. You can see how these components interact with each other.

Workflows

The workflow is an automated procedure that you add to your repository. Workflows are made up of one or more jobs and can be scheduled or triggered by an event. The workflow can be used to build, test, package, release, or deploy a project on GitHub.

Events

An event is a specific activity that triggers a workflow. For example, activity can originate from GitHub when someone pushes a commit to a repository or when an issue or pull request is created. You can also use the repository dispatch webhook to trigger a workflow when an external event occurs. For a complete list of events that can be used to trigger workflows, see Events that trigger workflows.

Jobs

A job is a set of steps that execute on the same runner. By default, a workflow with multiple jobs will run those jobs in parallel. You can also configure a workflow to run jobs sequentially. For example, a workflow can have two sequential jobs that build and test code, where the test job is dependent on the status of the build job. If the build job fails, the test job will not run.

Steps

A step is an individual task that can run commands in a job. A step can be either an action or a shell command. Each step in a job executes on the same runner, allowing the actions in that job to share data with each other.

Actions

Actions are standalone commands that are combined into steps to create a job. Actions are the smallest portable building block of a workflow. You can create your own actions, or use actions created by the GitHub community. To use an action in a workflow, you must include it as a step.

Runners

A runner is a server that has the GitHub Actions runner application installed. You can use a runner hosted by GitHub, or you can host your own. A runner listens for available jobs, runs one job at a time, and reports the progress, logs, and results back to GitHub. GitHub-hosted runners are based on Ubuntu Linux, Microsoft Windows, and macOS, and each job in a workflow runs in a fresh virtual environment. For information on GitHub-hosted runners, see "About GitHub-hosted runners." If you need a different operating system or require a specific hardware configuration, you can host your own runners. For information on self-hosted runners, see "Hosting your own runners."

Create an example workflow

GitHub Actions uses YAML syntax to define the events, jobs, and steps. These YAML files are stored in your code repository, in a directory called .github/workflows.

You can create an example workflow in your repository that automatically triggers a series of commands whenever code is pushed. In this workflow, GitHub Actions checks out the pushed code, installs the software dependencies, and runs bats -v.

1. In your repository, create the .github/workflows/ directory to store your workflow files.
2. In the .github/workflows/ directory, create a new file called learn-github-actions.yml and add the following code.

   name: learn-github-actions
   on: [push]
   jobs:
     check-bats-version:
       runs-on: ubuntu-latest
       steps:
         - uses: actions/checkout@v2
         - uses: actions/setup-node@v2
           with:
             node-version: '14'
         - run: npm install -g bats
         - run: bats -v
   

3. Commit these changes and push them to your GitHub repository.

Your new GitHub Actions workflow file is now installed in your repository and will run automatically each time someone pushes a change to the repository. For details about a job's execution history, see "Viewing the workflow's activity."

Understanding the workflow file

To help you understand how YAML syntax is used to create a workflow file, this section explains each line of the introduction's example:

name: learn-github-actions

on: [push]

jobs:

check-bats-version:

  runs-on: ubuntu-latest

  steps:

    - uses: actions/checkout@v2

    - uses: actions/setup-node@v2
      with:
        node-version: '14'

    - run: npm install -g bats

    - run: bats -v

Visualizing the workflow file

In this diagram, you can see the workflow file you just created and how the GitHub Actions components are organized in a hierarchy. Each step executes a single action or shell command. Steps 1 and 2 use prebuilt community actions. Steps 3 and 4 run shell commands directly on the runner. To find more prebuilt actions for your workflows, see "Finding and customizing actions."

Viewing the job's activity

Once your job has started running, you can view each step's activity on GitHub.

1. On your GitHub Enterprise Server instance, navigate to the main page of the repository.

2. Under your repository name, click Actions.

3. In the left sidebar, click the workflow you want to see.

4. Under "Workflow runs", click the name of the run you want to see.

5. Click on the job name to see the results of each step.

Next steps

To continue learning about GitHub Actions, see "Finding and customizing actions."

To understand how billing works for GitHub Actions, see "About billing for GitHub Actions".

Contacting support

If you need help with anything related to workflow configuration, such as syntax, GitHub-hosted runners, or building actions, look for an existing topic or start a new one in the GitHub Community Support's GitHub Actions category.

If you have feedback or feature requests for GitHub Actions, share those in the Feedback form for GitHub Actions.

Contact your site administrator for any of the following, whether your use or intended use falls into the usage limit categories:

• If you believe your account has been incorrectly restricted
• If you encounter an unexpected error when executing one of your Actions, for example: a unique ID
• If you encounter a situation where existing behavior contradicts expected, but not always documented, behavior