Ruby Cheat Sheet

Ruby cheat sheet with real commands and snippets for setup, core workflows, debugging, and production-safe automation patterns. If you are working across tools, pair this with the PHP Cheat Sheet and Regex Cheat Sheet.

Setup and Tooling

Goal: Install and verify language toolchain

# Run ruby command
ruby --version

# Run bundle command
bundle init

# Run bundle command
bundle install

Core Workflows

Goal: Run and build source code

# Execute ruby workflow
ruby app.rb

# Execute irb workflow
irb

Goal: Use a practical code snippet

# Simple service object pattern
class Greeter
  def initialize(name)
    @name = name
  end

  def call
    "Hello, #{@name}!"
  end
end

Testing and Formatting

Goal: Run automated tests

# Execute test-related command
bundle exec rspec

# Execute test-related command
bundle exec ruby test/test_app.rb

Goal: Run lint and formatter checks

# Execute quality command
bundle exec rubocop

# Execute quality command
bundle exec rubocop -A

Automation and CI

Goal: Create a repeatable CI shell step

# Run strict shell mode for CI step
set -euo pipefail

# Install dependencies deterministically
npm ci || pip install -r requirements.txt || true

# Run tests and fail fast on errors
bundle exec rspec

Debugging and Troubleshooting

Goal: Trace runtime issues

# Print runtime and package manager versions
node --version || python --version || true

# Search stack traces and TODO markers
rg "Traceback|Exception|TODO" .

# Re-run tests with verbose output
bundle exec rspec -v || bundle exec rspec --verbose || true

Common Gotchas

• Pin Ruby language/runtime versions in local and CI environments.
• Keep formatting and linting automated to avoid noisy diffs in code review.
• Prefer explicit dependency lock files for reproducible builds.
• Write small, deterministic tests that can run quickly in pre-commit checks.
• Document compiler/interpreter flags used in production builds.

Related Sheets

• PHP Cheat Sheet — daily PHP commands and production-ready examples.
• Regex Cheat Sheet — daily Regex commands and production-ready examples.
• Rust Cheat Sheet — daily Rust commands and production-ready examples.