GitHub Actions by Example: Context Expressions

As seen in Context Variables, you can inject variables into the workflow by using the ${{ <context variable> }} syntax. Workflows support evaluating expressions as well such as comparisons and simple functions. For more information see the docs.

 
name: expressions-example

on:

  push:

  pull_request:

jobs:

  use-expressions:

    strategy:

      matrix:

        greeting: [Hello, Howdy, Hey]

    runs-on: ubuntu-latest

    steps:

      -

        name: Print if 'Hello'

Use equality operators to get a boolean result; in this case we are only running the step when the greeting is “Hello”. Note the use of single quotes for the string literal. You can use ==, !=, <, <=, >, >=, &&, ||, and ( ... ). Learn more about operators here

 
        if: ${{ matrix.greeting == 'Hello' }}

        run: echo "greeting is Hello"

      -

        name: Print if starts with 'He'

        if: ${{ startsWith(matrix.greeting, 'He') }}

        run: echo "greeting starts with He"

      -

        name: Print if ends with 'y'

        if: ${{ endsWith(matrix.greeting, 'y') }}

        run: echo "greeting ends with y"          

      -

        name: Print if contains 'ow'

        if: ${{ contains(matrix.greeting, 'ow') }}

        run: echo "greeting contains ow"

      -

        name: Print formatted greeting

        run: |

                    echo "${{ format('{0} says {1}', github.actor, matrix.greeting) }}"

      -

        name: To JSON

toJSON() converts things to a pretty-printed JSON string

 
        run: echo 'Job context is ${{ toJSON(job) }}'

      -

        name: From JSON

fromJSON() converts a string into a JSON object or value

 
        env: ${{ fromJSON('{"FAVORITE_FRUIT": "APPLE", "FAVORITE_COLOR": "BLUE"}') }}

        run: echo "I would like a ${FAVORITE_COLOR} ${FAVORITE_FRUIT}"

      - 

        name: Success

success() returns true if no previous steps have failed or have been canceled.

 
        if: ${{ success() }}

        run: echo "Still running..."

      -

        name: Always

always() returns true no matter if a step failed or the workflow was cancelled.

 
        if: ${{ always() }}

        run: echo "You will always see this"

      -

        name: Canceled

canceled() returns true if the workflow was canceled.

 
        if: ${{ cancelled() }}

        run: echo "You canceled the workflow"

      -

        name: Failure

failure() returns true if any previous step failed.

 
        if: ${{ failure() }}

        run: echo "Something went wrong..."

By Ted Summer | Source | Inspired by Go by Example