I recently wrote a GitHub Actions workflow that I needed to be manually triggerable and scheduled via cron. My workflow had inputs. When the workflow is triggered by cron, I needed it to run with some default variables. When triggered manually, I wanted to allow the user to override some default values. It’s not immediately apparent how one should do this, but it is possible.

For example, I have the following GitHub Action workflow:

name: Print some text every 3rd minute
on:
  schedule:
    - cron: '1/3 * * * *'

jobs:
  print_text:
    runs-on: 'ubuntu-20.04'
    steps:
      -name: Print some text
       run: echo "Periodically printing passages"

It prints out:

Periodically printing passages

You can imagine a workflow that executes automated deployments to some test environment. What if I wanted to allow users of my GitHub repo to trigger this manually and print custom text, with a default message available? You can accomplish this in the same workflow by using environmental variables.

name: Print some text every 3rd minute
on:
  schedule:
    - cron: '1/3 * * * *'
  workflow_dispatch: # adding the workflow_dispatch so it can be triggered manually
    inputs:
      text_to_print:
        description: 'What text do you want to print?'
        required: true
        default: 'Periodically printing passages'

jobs:
  print_text:
    runs-on: 'ubuntu-20.04'
    steps:
      - name: Set the variables
        env:
          DEFAULT_MESSAGE: 'Periodically printing passages' # here is the default message
        run: echo "MESSAGE=${{ github.event.inputs.text_to_print || env.DEFAULT_MESSAGE }}" >> $GITHUB_ENV

      - name: Print some text
        run: echo "$MESSAGE" # prints the environmental variable, MESSAGE

I can trigger this in the Actions tag in GitHub:

I can manually trigger this workflow with some default text

The key to getting this to work is:

echo "MESSAGE=${{ github.event.inputs.text_to_print || env.DEFAULT_MESSAGE }}" >> $GITHUB_ENV

The preceding line chooses to assign the defined variable to the variable MESSAGE which is then injected into $GITHUB_ENV. We can reference it in the Print some text step.

Thanks for reading. ✊🏿