Gem installation with gem install in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of gem list after installing a gem

You run gem install colorize and then gem list. What will be part of the output?

Ruby

gem install colorize
 gem list

A colorize (1.0.0)

B colorize (not installed)

C colorize (0.8.1)

D No output related to colorize

💡 Hint

The gem list shows installed gems with their versions.

After installing the gem 'colorize', running 'gem list' will show it with its installed version, for example 'colorize (0.8.1)'.

🧠 Conceptual

intermediate

Understanding gem install options

Which gem install option installs a gem only for the current user, not system-wide?

A --local

B --system

C --global

D --user-install

💡 Hint

Think about installing gems without needing admin rights.

The --user-install option installs the gem in the user's home directory, avoiding system-wide changes.

🔧 Debug

advanced

Why does gem install fail with permission denied?

You run gem install rails and get a permission denied error. What is the most likely cause?

A The gem name is misspelled

B You need to run the command with sudo or use --user-install

C Ruby is not installed

D The internet connection is down

💡 Hint

Permission errors usually mean you lack rights to write to system folders.

Installing gems system-wide requires admin rights. Without them, permission denied errors occur.

📝 Syntax

advanced

Correct syntax to install a specific gem version

Which command correctly installs version 2.7.0 of the gem 'nokogiri'?

A gem install nokogiri -v 2.7.0

B gem install nokogiri --version=2.7.0

C gem install nokogiri --v 2.7.0

D gem install nokogiri version 2.7.0

💡 Hint

The short option for version is '-v'.

The correct syntax uses '-v' followed by the version number without '='.

🚀 Application

expert

How to install multiple gems in one command

You want to install 'rails' version 7.0.0 and 'puma' version 5.0.4 in one command. Which is correct?

A gem install rails -v 7.0.0 puma -v 5.0.4

B gem install rails:7.0.0 puma:5.0.4

C gem install rails --version 7.0.0 && gem install puma --version 5.0.4

D gem install rails -v7.0.0,puma -v5.0.4

💡 Hint

You can list multiple gems with their versions separated by spaces.

The correct syntax is to list each gem with its '-v' option separated by spaces in one command.

Practice

1. What does the command gem install do in Ruby?

easy

A. It installs a Ruby gem (library) on your system.

B. It runs Ruby code inside the gem file.

C. It updates Ruby to the latest version.

D. It removes a gem from your system.

Solution

1. Step 1: Understand the purpose of gem install

   This command is used to add new Ruby libraries (called gems) to your system so you can use them in your programs.

2. Step 2: Differentiate from other gem commands

   Running code, updating Ruby, or removing gems are done by other commands, not gem install.

3. Final Answer:

   It installs a Ruby gem (library) on your system. -> Option A

4. Quick Check:

   gem install = installs gem [OK]

Hint: Remember: install adds gems, require uses them [OK]

Common Mistakes:

• Confusing gem install with running Ruby code
• Thinking gem install updates Ruby itself
• Mixing up install with gem uninstall

2. Which of the following is the correct syntax to install the gem named nokogiri?

easy

A. ruby gem install nokogiri

B. install gem nokogiri

C. gem install nokogiri

D. gem add nokogiri

Solution

1. Step 1: Recall the standard gem installation syntax

   The correct command to install a gem is gem install gem_name, so for nokogiri it is gem install nokogiri.

2. Step 2: Identify incorrect syntax options

   Options like install gem, gem add, or prefixing with ruby are not valid commands.

3. Final Answer:

   gem install nokogiri -> Option C

4. Quick Check:

   Correct syntax = gem install [OK]

Hint: Use 'gem install' followed by gem name [OK]

Common Mistakes:

• Swapping order of 'gem' and 'install'
• Using 'gem add' instead of 'gem install'
• Adding 'ruby' before the command

3. What will happen if you run this command in the terminal?

gem install rails

medium

A. It will install the Rails gem and its dependencies on your system.

B. It will start a new Rails project in the current folder.

C. It will update the Rails gem to the latest version.

D. It will uninstall the Rails gem from your system.

Solution

1. Step 1: Understand the command purpose

   gem install rails installs the Rails gem and any required supporting gems on your computer.

2. Step 2: Differentiate from other Rails commands

   Starting a project uses rails new, updating uses gem update, and uninstalling uses gem uninstall.

3. Final Answer:

   It will install the Rails gem and its dependencies on your system. -> Option A

4. Quick Check:

   gem install rails = install gem [OK]

Hint: Install adds gems; creating projects uses 'rails new' [OK]

Common Mistakes:

• Confusing gem install with project creation
• Thinking gem install updates gems
• Assuming gem install removes gems

4. You tried to install a gem using gem install sinatra but got an error saying command not found: gem. What is the most likely cause?

medium

A. The gem name 'sinatra' is misspelled.

B. The gem is already installed, so it cannot be installed again.

C. You need to use ruby gem install sinatra instead.

D. You ran the command inside Ruby code instead of the terminal.

Solution

1. Step 1: Understand the error message

   The error command not found: gem means the system does not recognize the gem command where it was run.

2. Step 2: Identify correct usage context

   gem install must be run in the terminal (command line), not inside Ruby code or IRB.

3. Final Answer:

   You ran the command inside Ruby code instead of the terminal. -> Option D

4. Quick Check:

   Run gem commands in terminal, not Ruby code [OK]

Hint: Run gem commands in terminal, not inside Ruby scripts [OK]

Common Mistakes:

• Trying to run gem install inside Ruby code
• Adding 'ruby' before gem install command
• Assuming gem install fails if gem exists

5. You want to install the gem httparty but only for your current project, not system-wide. Which command should you use?

hard

A. gem install httparty --global

B. gem install httparty --user-install

C. gem install httparty --system

D. gem install httparty --local

Solution

1. Step 1: Understand gem installation scopes

   By default, gem install installs gems system-wide. To install only for the current user (project scope), use --user-install.

2. Step 2: Eliminate incorrect options

   --system installs system-wide, --global is not a valid gem option, and --local installs from local files, not scope.

3. Final Answer:

   gem install httparty --user-install -> Option B

4. Quick Check:

   Use --user-install for user-only gem install [OK]

Hint: Add --user-install to install gem only for current user [OK]

Common Mistakes:

• Using --system to limit install scope
• Confusing --local with user install
• Assuming --global is a valid option