GitHub Actions Workflow Syntax: ‘shell’ – Specifying the Shell for Your Commands

In the ecosystem of GitHub Actions, the ‘shell’ keyword plays a crucial role in defining the execution environment for your commands. This blog post will cover the ‘shell’ keyword in the GitHub Actions Workflow syntax, explaining its syntax, demonstrating its usage, and providing examples.

Introduction

GitHub Actions Workflows enable automation of software development processes such as building, testing, and deploying applications. Workflows are composed of ‘jobs’ and ‘steps’, where each job contains steps that perform specific tasks. When a command is to be run in a step, the ‘shell’ keyword can be used to specify which shell is used for that command.

Understanding the ‘shell’ Syntax

In GitHub Actions Workflow syntax, the ‘shell’ keyword is used within a step to specify the type of shell that executes the commands in the ‘run’ context.

Here is a basic structure of how ‘shell’ is used within a step:

jobs:
  job_id:
    runs-on: runner_type
    steps:
    - name: Step name
      run: command
      shell: shell_type

jobs:

job_id:

runs-on: runner_type

steps:

- name: Step name

run: command

shell: shell_type

In this syntax, ‘shell_type’ is one of the supported shell types (e.g., bash, sh, cmd, powershell, etc.) that you want to use to execute the command. If not specified, GitHub Actions will use the default shell for the runner’s operating system.

Example of ‘shell’ in a Workflow

To illustrate the ‘shell’ keyword, let’s consider a workflow where a script is executed using PowerShell on a Windows runner:

name: PowerShell CI

on: [push]

jobs:
  build:
    runs-on: windows-latest
    steps:
    - name: Checkout code
      uses: actions/checkout@v2
    - name: Execute script
      run: .\script.ps1
      shell: powershell

name: PowerShell CI

on: [push]

jobs:

build:

runs-on: windows-latest

steps:

- name: Checkout code

uses: actions/checkout@v2

- name: Execute script

run: .\script.ps1

shell: powershell

In this workflow, the ‘build’ job consists of two steps. The first step checks out the code using the actions/checkout@v2 action. The second step uses the ‘shell’ keyword to specify that the script is to be run using PowerShell.

Conclusion

The ‘shell’ keyword in GitHub Actions Workflow syntax gives developers control over the shell environment in which commands are executed. This level of control can be essential when scripts require a specific shell, or when optimizing the environment for performance or compatibility reasons.