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Understanding GitHub Actions

Learn the basics of GitHub Actions, including core concepts and essential terminology.


GitHub Actions is a continuous integration and continuous delivery (CI/CD) platform that allows you to automate your build, test, and deployment pipeline. You can create workflows that build and test every pull request to your repository, or deploy merged pull requests to production.

GitHub Actions goes beyond just DevOps and lets you run workflows when other events happen in your repository. For example, you can run a workflow to automatically add the appropriate labels whenever someone creates a new issue in your repository.

GitHub provides Linux, Windows, and macOS virtual machines to run your workflows, or you can host your own self-hosted runners in your own data center or cloud infrastructure.

For more information about introducing GitHub Actions to your enterprise, see "Introducing GitHub Actions to your enterprise."

GitHub Actions のコンポーネント

You can configure a GitHub Actions workflow to be triggered when an event occurs in your repository, such as a pull request being opened or an issue being created. Your workflow contains one or more jobs which can run in sequential order or in parallel. Each job will run inside its own virtual machine runner, or inside a container, and has one or more steps that either run a script that you define or run an action, which is a reusable extension that can simplify your workflow.



A workflow is a configurable automated process that will run one or more jobs. Workflows are defined by a YAML file checked in to your repository and will run when triggered by an event in your repository, or they can be triggered manually, or at a defined schedule.

Workflows are defined in the .github/workflows directory in a repository, and a repository can have multiple workflows, each of which can perform a different set of tasks. For example, you can have one workflow to build and test pull requests, another workflow to deploy your application every time a release is created, and still another workflow that adds a label every time someone opens a new issue.

You can reference a workflow within another workflow, see "Reusing workflows."

For more information about workflows, see "Using workflows."


An event is a specific activity in a repository that triggers a workflow run. For example, activity can originate from GitHub when someone creates a pull request, opens an issue, or pushes a commit to a repository. You can also trigger a workflow run on a schedule, by posting to a REST API, or manually.



A job is a set of steps in a workflow that execute on the same runner. Each step is either a shell script that will be executed, or an action that will be run. Steps are executed in order and are dependent on each other. Since each step is executed on the same runner, you can share data from one step to another. For example, you can have a step that builds your application followed by a step that tests the application that was built.

You can configure a job's dependencies with other jobs; by default, jobs have no dependencies and run in parallel with each other. When a job takes a dependency on another job, it will wait for the dependent job to complete before it can run. For example, you may have multiple build jobs for different architectures that have no dependencies, and a packaging job that is dependent on those jobs. The build jobs will run in parallel, and when they have all completed successfully, the packaging job will run.

For more information about jobs, see "Using jobs."


An action is a custom application for the GitHub Actions platform that performs a complex but frequently repeated task. Use an action to help reduce the amount of repetitive code that you write in your workflow files. An action can pull your git repository from GitHub, set up the correct toolchain for your build environment, or set up the authentication to your cloud provider.

You can write your own actions, or you can find actions to use in your workflows in the GitHub Marketplace.

To share actions across your enterprise without publishing the actions publicly, you can store the actions in an internal repository, then configure the repository to allow access to GitHub Actions workflows in other repositories owned by the same organization or by any organization in the enterprise. For more information, see "Sharing actions and workflows with your enterprise."



A runner is a server that runs your workflows when they're triggered. Each runner can run a single job at a time. GitHub provides Ubuntu Linux, Microsoft Windows, and macOS runners to run your workflows; each workflow run executes in a fresh, newly-provisioned virtual machine. If you need a different operating system or require a specific hardware configuration, you can host your own runners. For more information about self-hosted runners, see "Hosting your own runners."


GitHub Actions uses YAML syntax to define the workflow. Each workflow is stored as a separate YAML file in your code repository, in a directory named .github/workflows.

コードがプッシュされるたびに一連のコマンドを自動的にトリガーするサンプルワークフローをリポジトリに作成できます。 In this workflow, GitHub Actions checks out the pushed code, installs the bats testing framework, and runs a basic command to output the bats version: bats -v.

  1. リポジトリに、ワークフローファイルを保存するための .github/workflows/ ディレクトリを作成します。

  2. .github/workflows/ ディレクトリに、learn-github-actions.yml という名前の新しいファイルを作成し、次のコードを追加します。

    name: learn-github-actions
    on: [push]
        runs-on: ubuntu-latest
          - uses: actions/checkout@v3
          - uses: actions/setup-node@v3
              node-version: '14'
          - run: npm install -g bats
          - run: bats -v
  3. これらの変更をコミットして、GitHub リポジトリにプッシュします。

これで、新しい GitHub Actions ワークフローファイルがリポジトリにインストールされ、別のユーザがリポジトリに変更をプッシュするたびに自動的に実行されます。 To see the details about a workflow's execution history, see "Viewing the activity for a workflow run."


YAML 構文を使用してワークフローファイルを作成する方法を理解しやすくするために、このセクションでは、導入例の各行について説明します。

name: learn-github-actions
オプション - GitHub リポジトリの [Actions] タブに表示されるワークフローの名前。
on: [push]
Specifies the trigger for this workflow. This example uses the push event, so a workflow run is triggered every time someone pushes a change to the repository or merges a pull request. This is triggered by a push to every branch; for examples of syntax that runs only on pushes to specific branches, paths, or tags, see "Workflow syntax for GitHub Actions."
Groups together all the jobs that run in the learn-github-actions workflow.
Defines a job named check-bats-version. The child keys will define properties of the job.
  runs-on: ubuntu-latest
Configures the job to run on the latest version of an Ubuntu Linux runner. これは、ジョブが GitHub によってホストされている新しい仮想マシンで実行されるということです。 For syntax examples using other runners, see "Workflow syntax for GitHub Actions."
check-bats-version ジョブで実行されるすべてのステップをグループ化します。 Each item nested under this section is a separate action or shell script.
    - uses: actions/checkout@v3
The uses keyword specifies that this step will run v3 of the actions/checkout action. This is an action that checks out your repository onto the runner, allowing you to run scripts or other actions against your code (such as build and test tools). You should use the checkout action any time your workflow will run against the repository's code.
    - uses: actions/setup-node@v3
        node-version: '14'
This step uses the actions/setup-node@v3 action to install the specified version of the Node.js (this example uses v14). This puts both the node and npm commands in your PATH.
    - run: npm install -g bats
run キーワードは、ランナーでコマンドを実行するようにジョブに指示します。 この場合、npm を使用して bats ソフトウェアテストパッケージをインストールしています。
    - run: bats -v
最後に、ソフトウェアバージョンを出力するパラメータを指定して bats コマンドを実行します。


この図では、作成したワークフローファイルと、GitHub Actions コンポーネントが階層にどのように整理されているかを確認できます。 Each step executes a single action or shell script. Steps 1 and 2 run actions, while steps 3 and 4 run shell scripts. ワークフローのビルド済みアクションの詳細については、「アクションの検索とカスタマイズ」を参照してください。


Viewing the activity for a workflow run

When your workflow is triggered, a workflow run is created that executes the workflow. After a workflow run has started, you can see a visualization graph of the run's progress and view each step's activity on GitHub.

  1. GitHub.comで、リポジトリのメインページにアクセスしてください。

  2. リポジトリ名の下でActions(アクション)をクリックしてください。


  3. 左のサイドバーで、表示させたいワークフローをクリックしてください。


  4. "Workflow runs(ワークフローの実行)"の下で、表示させたい実行の名前をクリックしてください。


  5. [Jobs] または視覚化グラフで、表示するジョブをクリックします。


  6. View the results of each step.


More complex examples

For examples that demonstrate more complex features of GitHub Actions, see "Examples." You can see detailed examples that explain how to test your code on a runner, access the GitHub CLI, and use advanced features such as concurrency and test matrices.



たとえば構文、GitHubホストランナー、アクションの構築など、ワークフローの設定に関して何か支援が必要な場合は、GitHub Community SupportのGitHub Actionsカテゴリで既存のトピックを探してみるか、新しいトピックを開始してください。

GitHub Actionsについてのフィードバックもしくは機能リクエストがあるなら、それらをFeedback discussion for GitHub Actionsで共有してください。

あなたの利用方法、もしくは意図する利用方法が利用制限のカテゴリに当てはまるかどうかに関わらず、以下のいずれかの場合はGitHub Supportに連絡してください。

  • アカウントに間違った制約が課されていると思われる場合
  • たとえばユニークIDのような予想外のエラーに、アクションの実行時に遭遇した場合
  • 既存の動作が期待される、ただし必ずしもドキュメント化されてはいない動作と矛盾するような状況に遭遇した場合