creating-a-composite-action.md

title	shortTitle	intro	redirect_from	versions	type	defaultPlatform	topics
Creating a composite action	Create a composite action	In this guide, you'll learn how to build a composite action.	/actions/creating-actions/creating-a-composite-run-steps-action /actions/creating-actions/creating-a-composite-action	fpt ghes ghec * * *	tutorial	linux	Action development

{% data reusables.actions.enterprise-github-hosted-runners %}

Introduction

In this guide, you'll learn about the basic components needed to create and use a packaged composite action. To focus this guide on the components needed to package the action, the functionality of the action's code is minimal. The action prints "Hello World" and then "Goodbye", or if you provide a custom name, it prints "Hello [who-to-greet]" and then "Goodbye". The action also maps a random number to the random-number output variable, and runs a script named goodbye.sh.

Once you complete this project, you should understand how to build your own composite action and test it in a workflow.

{% data reusables.actions.context-injection-warning %}

Composite actions and reusable workflows

Composite actions allow you to collect a series of workflow job steps into a single action which you can then run as a single job step in multiple workflows. Reusable workflows provide another way of avoiding duplication, by allowing you to run a complete workflow from within other workflows. For more information, see AUTOTITLE.

Prerequisites

Before you begin, you'll create a repository on {% data variables.product.github %}.

1. Create a new public repository on {% data variables.product.github %}. You can choose any repository name, or use the following hello-world-composite-action example. You can add these files after your project has been pushed to {% data variables.product.product_name %}. For more information, see AUTOTITLE.

2. Clone your repository to your computer. For more information, see AUTOTITLE.

3. From your terminal, change directories into your new repository.

   cd hello-world-composite-action

4. In the hello-world-composite-action repository, create a new file called goodbye.sh with example code:

   echo "echo Goodbye" > goodbye.sh

5. From your terminal, make goodbye.sh executable. {% linux %}

   {% data reusables.actions.composite-actions-executable-linux-mac %}

   {% endlinux %} {% mac %}

   {% data reusables.actions.composite-actions-executable-linux-mac %}

   {% endmac %} {% windows %}

   git add --chmod=+x -- goodbye.sh

   {% endwindows %}

6. From your terminal, check in your goodbye.sh file.

   {% linux %}

   {% data reusables.actions.composite-actions-commit-file-linux-mac %}

   {% endlinux %} {% mac %}

   {% data reusables.actions.composite-actions-commit-file-linux-mac %} {% endmac %} {% windows %}

   git commit -m "Add goodbye script"
   git push

   {% endwindows %}

Creating an action metadata file

1. In the hello-world-composite-action repository, create a new file called action.yml and add the following example code. For more information about this syntax, see AUTOTITLE.

   name: 'Hello World'
   description: 'Greet someone'
   inputs:
     who-to-greet:  # id of input
       description: 'Who to greet'
       required: true
       default: 'World'
   outputs:
     random-number:
       description: "Random number"
       value: {% raw %}${{ steps.random-number-generator.outputs.random-number }}{% endraw %}
   runs:
     using: "composite"
     steps:
       - name: Set Greeting
         run: echo "Hello $INPUT_WHO_TO_GREET."
         shell: bash
         env:
           INPUT_WHO_TO_GREET: {% raw %}${{ inputs.who-to-greet }}{% endraw %}
   
       - name: Random Number Generator
         id: random-number-generator
         run: echo "random-number=$(echo $RANDOM)" >> $GITHUB_OUTPUT
         shell: bash
   
       - name: Set GitHub Path
         run: echo "$GITHUB_ACTION_PATH" >> $GITHUB_PATH
         shell: bash
         env:
           GITHUB_ACTION_PATH: {% raw %}${{ github.action_path }}{% endraw %}
   
       - name: Run goodbye.sh
         run: goodbye.sh
         shell: bash
   

   This file defines the who-to-greet input, maps the random generated number to the random-number output variable, adds the action's path to the runner system path (to locate the goodbye.sh script during execution), and runs the goodbye.sh script.

   For more information about managing outputs, see AUTOTITLE.

   For more information about how to use github.action_path, see AUTOTITLE.

2. From your terminal, check in your action.yml file.

   git add action.yml
   git commit -m "Add action"
   git push

3. From your terminal, add a tag. This example uses a tag called v1. For more information, see AUTOTITLE.

   git tag -a -m "Description of this release" v1
   git push --follow-tags

Testing out your action in a workflow

The following workflow code uses the completed hello world action that you made in AUTOTITLE.

Copy the workflow code into a .github/workflows/main.yml file in another repository, replacing OWNER and SHA with the repository owner and the SHA of the commit you want to use, respectively. You can also replace the who-to-greet input with your name.

on: [push]

jobs:
  hello_world_job:
    runs-on: ubuntu-latest
    name: A job to say hello
    steps:
      - uses: {% data reusables.actions.action-checkout %}
      - id: foo
        uses: OWNER/hello-world-composite-action@SHA
        with:
          who-to-greet: 'Mona the Octocat'
      - run: echo random-number "$RANDOM_NUMBER"
        shell: bash
        env:
          RANDOM_NUMBER: {% raw %}${{ steps.foo.outputs.random-number }}{% endraw %}

From your repository, click the Actions tab, and select the latest workflow run. The output should include: "Hello Mona the Octocat", the result of the "Goodbye" script, and a random number.

Example composite actions on {% data variables.product.github %}

You can find many examples of composite actions on {% data variables.product.github %}.

• microsoft/action-python
• microsoft/gpt-review
• tailscale/github-action