Bundle exec for isolated execution in Ruby - Mini Project: Build & Apply

Bundle exec for isolated execution

📖 Scenario: You are working on a Ruby project that uses gems (libraries) to add extra features. Sometimes, different projects need different versions of the same gem. To avoid conflicts, Ruby developers use bundle exec to run commands in an isolated environment where only the gems listed in the project's Gemfile are used.

🎯 Goal: You will create a simple Ruby script and a Gemfile to manage gem versions. Then, you will use bundle exec to run the script with the correct gem versions, ensuring isolated execution.

📋 What You'll Learn

Create a Gemfile with a specific gem and version

Create a Ruby script that uses the gem

Use bundle exec to run the Ruby script

Print output showing the gem version used

💡 Why This Matters

🌍 Real World

Many Ruby projects use Bundler to manage gem versions and dependencies. Using <code>bundle exec</code> ensures your code runs with the correct gems, avoiding conflicts.

💼 Career

Understanding Bundler and isolated execution is important for Ruby developers working on projects with multiple dependencies or when deploying applications.

1

Create a Gemfile with the colorize gem version 0.8.1

Create a file called Gemfile with the exact content:
source 'https://rubygems.org'
gem 'colorize', '0.8.1'

Ruby

# Create a Gemfile with source and gem 'colorize' version '0.8.1'
# Your code here

Hint

The Gemfile tells Bundler which gems and versions to use.

2

Create a Ruby script color_test.rb that uses the colorize gem

Create a file called color_test.rb with these lines:
require 'colorize'
puts 'Hello, Bundler!'.colorize(:green)

Ruby

# Create color_test.rb with require and puts using colorize
# Your code here

Hint

The script uses require 'colorize' to load the gem and prints colored text.

3

Install gems and set a variable to run the script with bundle exec

Run bundle install in your terminal to install gems. Then, create a variable called command and set it to the string 'bundle exec ruby color_test.rb'.

Ruby

# Set command variable to run script with bundle exec
# Your code here

Hint

The command variable holds the exact command to run the script with Bundler's isolated environment.

4

Run the command and print the output

Use output = `#{command}` to run the command and capture the output. Then, print the output variable.

Ruby

# Run the command and print output
# Your code here

Hint

Use backticks ` to run the command and capture its output, then print it.

Practice

1.

What is the main purpose of using bundle exec in a Ruby project?

easy

A. To create a new Ruby project with default settings

B. To update all gems to their latest versions globally

C. To uninstall unused gems from the system

D. To run commands using only the gems specified in the project's Gemfile

Solution

1. Step 1: Understand the role of bundle exec

   bundle exec runs commands using the gems listed in the project's Gemfile, isolating from other system gems.

2. Step 2: Compare options

   Options B, C, and D describe different gem or project management tasks unrelated to isolated execution.

3. Final Answer:

   To run commands using only the gems specified in the project's Gemfile -> Option D

4. Quick Check:

   bundle exec isolates gems = A [OK]

Hint: Remember: bundle exec uses project gems only, avoiding conflicts [OK]

Common Mistakes:

• Thinking bundle exec updates gems
• Confusing bundle exec with gem uninstall
• Assuming bundle exec creates projects

2.

Which of the following is the correct syntax to run a Ruby script app.rb using bundle exec?

easy

A. bundle exec ruby app.rb

B. ruby bundle exec app.rb

C. bundle ruby exec app.rb

D. exec bundle ruby app.rb

Solution

1. Step 1: Recall correct command order

   The correct syntax places bundle exec before the command to run, here ruby app.rb.

2. Step 2: Validate options

   Only bundle exec ruby app.rb correctly places bundle exec before ruby app.rb. Others mix order incorrectly.

3. Final Answer:

   bundle exec ruby app.rb -> Option A

4. Quick Check:

   bundle exec before command = C [OK]

Hint: Put 'bundle exec' right before the command you want to run [OK]

Common Mistakes:

• Swapping order of bundle exec and ruby
• Inserting exec or bundle in wrong places
• Omitting bundle exec entirely

3.

Given a Ruby project with a Gemfile specifying rspec version 3.10.0, what will be the output of running rspec --version vs bundle exec rspec --version if the system has rspec 4.0.0 installed globally?

medium

A. rspec --version shows 4.0.0, bundle exec rspec --version shows 3.10.0

B. rspec --version shows 3.10.0, bundle exec rspec --version shows 4.0.0

C. Both commands show 4.0.0

D. Both commands show 3.10.0

Solution

1. Step 1: Understand gem version usage

   Running rspec --version uses the system's global gem version, which is 4.0.0 here.

2. Step 2: Effect of bundle exec

   bundle exec rspec --version runs using the project's Gemfile version, 3.10.0, isolating from global gems.

3. Final Answer:

   rspec --version shows 4.0.0, bundle exec rspec --version shows 3.10.0 -> Option A

4. Quick Check:

   bundle exec uses Gemfile version = D [OK]

Hint: Without bundle exec uses global gems; with it uses project gems [OK]

Common Mistakes:

• Assuming both commands show same version
• Confusing global and project gem versions
• Ignoring Gemfile gem isolation

4.

Consider this command run inside a Ruby project folder:
rspec spec/test_spec.rb
The test fails due to a gem version conflict. How can you fix this using bundle exec?

medium

A. Run gem install rspec to update the gem globally

B. Run bundle exec rspec spec/test_spec.rb to use project gems

C. Run rspec --update to fix conflicts automatically

D. Delete the Gemfile and try again

Solution

1. Step 1: Identify cause of failure

   Failure is due to gem version conflict between global and project gems.

2. Step 2: Use bundle exec to isolate gems

   Running bundle exec rspec spec/test_spec.rb forces use of project Gemfile gems, resolving conflicts.

3. Final Answer:

   Run bundle exec rspec spec/test_spec.rb to use project gems -> Option B

4. Quick Check:

   bundle exec fixes gem conflicts = A [OK]

Hint: Use bundle exec before commands to fix gem conflicts [OK]

Common Mistakes:

• Trying to update gems globally instead of isolating
• Using invalid rspec options
• Deleting Gemfile which breaks project setup

5.

You have a Ruby project with multiple gems and versions specified in the Gemfile. You want to run a custom Ruby script script.rb that depends on these gems. Which command ensures your script uses the correct gem versions and avoids conflicts?

hard

A. ruby script.rb

B. gem install script.rb

C. bundle exec ruby script.rb

D. bundle install script.rb

Solution

1. Step 1: Understand gem version isolation need

   Running ruby script.rb alone may use system gems, causing version conflicts.

2. Step 2: Use bundle exec to run script with project gems

   bundle exec ruby script.rb runs the script using gems specified in the Gemfile, ensuring correct versions.

3. Step 3: Eliminate incorrect options

   gem install script.rb and bundle install script.rb are invalid commands for running scripts.

4. Final Answer:

   bundle exec ruby script.rb -> Option C

5. Quick Check:

   Use bundle exec to run scripts with project gems = B [OK]

Hint: Always prefix scripts with bundle exec to use project gems [OK]

Common Mistakes:

• Running scripts without bundle exec causing conflicts
• Confusing gem install with running scripts
• Trying to bundle install a script file