Bash

🧪 ShellCheck + GitHub Actions (CI for Bash)

ShellCheck is a static analysis tool for shell scripts. It warns you about syntax errors, bad practices, and potential bugs.

This guide shows how to:

• Use shellcheck locally
• Automate it with GitHub Actions
• Enforce quality checks in pull requests

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🛠️ What is ShellCheck?

ShellCheck analyzes Bash scripts and reports:

• Quoting issues
• Deprecated syntax
• Unset variables
• Unsafe redirects
• Logical errors

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🔧 1. Installing ShellCheck

✅ Ubuntu / Debian

sudo apt install shellcheck

✅ macOS (Homebrew)

brew install shellcheck

✅ Manual (Portable)

Download from: https://github.com/koalaman/shellcheck/releases

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🧪 2. Using ShellCheck Locally

Run it on a script:

shellcheck script.sh

To check all scripts in your repo:

find . -name "*.sh" -exec shellcheck {} \;

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🚀 3. GitHub Actions: shellcheck.yml

➕ Add Workflow File

Create .github/workflows/shellcheck.yml:

name: ShellCheck Linter

on:
  push:
    paths:
      - '**.sh'
  pull_request:
    paths:
      - '**.sh'

jobs:
  lint:
    runs-on: ubuntu-latest

    steps:
    - name: Checkout repository
      uses: actions/checkout@v3

    - name: Install ShellCheck
      run: sudo apt-get install -y shellcheck

    - name: Run ShellCheck
      run: |
        find . -name "*.sh" | xargs shellcheck

✅ Features:

• Lints all .sh files on push/PR
• Fails if any warnings are detected

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🧠 Example Output

In script.sh line 4:
for f in $(ls *.txt); do
         ^-- SC2045: Iterating over ls output is fragile. Use globs.

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🧹 Best Practices

Practice	Why
Fix all shellcheck warnings	Improve reliability
Run on every PR	Maintain quality
Use consistent quoting	Prevent bugs
Enable set -euo pipefail in scripts	Add extra safety

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📚 References

• ShellCheck homepage
• ShellCheck GitHub
• Awesome ShellCheck Tips

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📁 File: advance/shellcheck-ci.md
Author: Kashif Alam

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