Sinatra Setup for Beginners

Version: v0.18.0

When to Use

• User wants Sinatra web application
• Beginner needs Sinatra environment setup
• User asks "How do I set up Sinatra?"

Instructions for ASSISTANT

Format ALL instructions as Claude Code copy/paste blocks.

DO NOT: Manual instructions like "Open File Explorer", "Navigate to folder" ALWAYS: Single code block with TASK, STEPs, and report request

Setup Steps

1. Verify Ruby

ruby --version

Expected: Ruby 3.0+ | If missing:

• Windows: RubyInstaller from rubyinstaller.org
• Mac: brew install ruby
• Linux: sudo apt-get install ruby-full

2. Install Bundler

gem install bundler

What: Ruby's package manager Verify: bundler --version shows 2.X.X

3. Create Gemfile

File: Gemfile (no extension, capital G) in project root

source 'https://rubygems.org'
gem 'sinatra'

4. Install Dependencies

bundle install

Wait: 30-90 seconds Creates: Gemfile.lock

5. Create app.rb

my-project/
├── Gemfile
├── Gemfile.lock
└── app.rb  ← Create here

6. Verify Installation

ruby --version
bundle --version
bundle list
ruby -e "require 'sinatra'; puts 'Sinatra works!'"

Project Structure

my-project/
├── Gemfile        ← Dependencies
├── Gemfile.lock   ← Version lock
├── app.rb         ← Main code
├── views/         ← Templates (.erb)
└── public/        ← Static files

Troubleshooting

Next Steps

After setup: Create first route, start server, build first page.

Remember: Run bundle exec ruby app.rb to start (ensures correct gem versions).

End of Skill