Introduction to GitHub Actions
You can read the full tutorial here: https://towardsdatascience.com/introduction-to-github-actions-7fcb30d0f959
Actions vs. Workflows
Actions are individual tasks and workflows are custom automated processes
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Workflows: automated processes that run on your repository; workflows can have many GitHub Actions
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GitHub Actions: individual tasks; they can be written using Docker, JavaScript and now also shell scrips with the new Composite Run Steps; you can write your own actions or use an action someone else created
Writing your first workflow
Workflows are defined using YAML files and you must store them in the .github/workflows directory of your repository.
To create a workflow we need to define these things:
- The event that triggers the workflow
- The machine each job should run
- The jobs that make the workflow (jobs contain a set of steps that perform individual tasks and run in parallel by default)
- The steps each job should run
# your-repo-name/.github/workflows/first_workflow.yml
name: First Workflow
on: push
jobs:
first-job:
name: Say hi
runs-on: ubuntu-latest
steps:
- name: Print a greeting
run: echo Hi from our first workflow!Using an Action in your workflow
Actions are individual tasks and we can use them from three sources:
- Actions defined in the same repository as the workflow
- Actions defined in a public repository
- Actions defined in an published Docker container image
Let's use an Action that prints ASCII art text:
# your-repo-name/.github/workflows/first_workflow.yml
name: First Workflow
on: push
jobs:
first-job:
name: Say hi
runs-on: ubuntu-latest
steps:
- name: Print a greeting
run: echo Hi from our first workflow!
- name: Show ASCII greeting
uses: mscoutermarsh/ascii-art-action@master
with:
text: 'HELLO!'Using Python with workflows
Setting a specific version of Python or PyPy is the recommended way of using Python with GitHub Actions. To do that we'll use an action: setup-python. In this example we'll run a Python script defined in the same repository as the workflow. To do that we also need to use the checkout action to access the file.
# your-repo-name/.github/workflows/first_workflow.yml
name: First Workflow
on: push
jobs:
get-posts-job:
name: Get TDS posts
runs-on: ubuntu-latest
steps:
- name: Check-out the repo under $GITHUB_WORKSPACE
uses: actions/checkout@v2
- name: Set up Python 3.8
uses: actions/setup-python@v2
with:
python-version: '3.8'
- name: Install Scrapy
run: pip install scrapy
- name: Get TDS posts about GitHub Actions
run: scrapy runspider posts_spider.py -o posts.jsonPersisting workflow data
An artifact is a file or collection of files produced during a workflow run. We can pass an artifact to another job in the same workflow or download it using the GitHub UI. To work with artifacts we use the upload-artifact and download-artifact actions.
# your-repo-name/.github/workflows/first_workflow.yml
name: First Workflow
on: push
jobs:
get-posts-job:
name: Get TDS posts
runs-on: ubuntu-latest
steps:
- name: Check-out the repo under $GITHUB_WORKSPACE
uses: actions/checkout@v2
- name: Set up Python 3.8
uses: actions/setup-python@v2
with:
python-version: '3.8'
- name: Install Scrapy
run: pip install scrapy
- name: Get TDS posts about GitHub Actions
run: scrapy runspider posts_spider.py -o posts.json
- name: Upload artifact
uses: actions/upload-artifact@v2
with:
name: posts
path: posts.jsonYou can download the file using the GitHub UI.
Creating your first Action
Actions can be created using Docker containers, JavaScript or you can create an action using shell scripts (a composite run steps action). The main use case for the composite run steps action is when you have a lot of shell scripts to automate tasks and writing a shell script to combine them is easier than JavaScript or Docker.
The filename for an action must be either action.yml or action.yaml. Let's use the example from GitHub Docs and create an action that prints a "Hey [user]" message. Since it's a composite action we'll use the using: "composite" syntax:
# action.yml
name: 'Hey From a GitHub Action'
description: 'Greet someone'
inputs:
user: # id of input
description: 'Who to greet'
required: true
default: 'You'
runs:
using: "composite"
steps:
- run: echo Hey ${{ inputs.user }}.
shell: bashIf an action is defined in the same repository as the workflow we can refer to it using ./path-to-action-file. In this case we need to access the file inside the repository, so we also need to use the checkout action.
Running an action from the same repository
# .github/workflows/use-action-same-repo.yml
name: Action from the same repo
on: push
jobs:
use-your-own-action:
name: Say Hi using your own action
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v2
- uses: ./ # the action.yml file is in the root folder
with:
user: 'Déborah'Running an action from a public repository
# .github/workflows/use-action-public-repo.yml
name: Action from a public repository
on: push
jobs:
use-your-own-action:
name: Say Hi using your own action
runs-on: ubuntu-latest
steps:
- uses: dmesquita/github-actions-tutorial@master
with:
user: 'Déborah'