Running scripts with ruby command - Mini Project: Build & Apply

Running Ruby Scripts with the ruby Command

📖 Scenario: You want to learn how to run simple Ruby scripts using the ruby command in the terminal. This is useful when you write Ruby code in a file and want to see the output by running it.

🎯 Goal: Learn how to create a Ruby script file, add a simple Ruby program, and run it using the ruby command to see the output.

📋 What You'll Learn

Create a Ruby script file named greeting.rb

Write a Ruby program that prints a greeting message

Use the ruby command to run the script and display the output

💡 Why This Matters

🌍 Real World

Running Ruby scripts from files is how developers test and run their Ruby programs in real projects.

💼 Career

Knowing how to run Ruby scripts with the ruby command is essential for Ruby developers, testers, and anyone working with Ruby code.

1

Create a Ruby script file with a greeting message

Create a Ruby script file named greeting.rb and write this exact line of code inside it: puts "Hello, Ruby!"

Ruby

# Create a file named greeting.rb and write the code below
# puts "Hello, Ruby!"

Hint

Use a text editor to create a file named greeting.rb and type puts "Hello, Ruby!" inside it.

2

Add a variable to store the greeting message

In the greeting.rb file, add a variable named message and set it to the string "Hello, Ruby!". Then use puts message to print it.

Ruby

message = "Hello, Ruby!"
puts message
# Your code here

Hint

Assign the string to message and then print it with puts message.

3

Run the Ruby script using the ruby command

Open your terminal or command prompt and run the command ruby greeting.rb to execute the script and see the output.

Ruby

# Run the script in your terminal with: ruby greeting.rb

Hint

Use the terminal command ruby greeting.rb to run your script file.

4

Display the output of the Ruby script

Print the output of running ruby greeting.rb. It should show the exact text: Hello, Ruby!

Ruby

# Print the output below
# Your code here

Hint

When you run ruby greeting.rb, the terminal should display Hello, Ruby!.

Practice

1. What does the ruby command do when used in the terminal?

easy

A. It runs a Ruby script saved in a file.

B. It compiles Ruby code into an executable.

C. It opens the Ruby interactive console.

D. It installs Ruby gems automatically.

Solution

1. Step 1: Understand the purpose of the ruby command

   The ruby command is used to run Ruby scripts saved in files from the terminal.

2. Step 2: Differentiate from other Ruby tools

   It does not compile code, open the console, or install gems automatically.

3. Final Answer:

   It runs a Ruby script saved in a file. -> Option A

4. Quick Check:

   ruby command runs scripts = A [OK]

Hint: ruby command runs saved scripts, not compilers or consoles [OK]

Common Mistakes:

• Confusing ruby command with irb (interactive console)
• Thinking ruby compiles code to executables
• Assuming ruby installs gems automatically

2. Which of the following is the correct way to run a Ruby script named hello.rb from the terminal?

easy

A. run hello.rb

B. start ruby hello.rb

C. execute hello.rb

D. ruby hello.rb

Solution

1. Step 1: Identify the correct command syntax

   The correct syntax to run a Ruby script is ruby filename.rb.

2. Step 2: Check each option

   Only ruby hello.rb matches the correct syntax.

3. Final Answer:

   ruby hello.rb -> Option D

4. Quick Check:

   Use ruby + filename.rb to run scripts [OK]

Hint: Use 'ruby filename.rb' to run scripts in terminal [OK]

Common Mistakes:

• Using 'run' or 'execute' commands which don't exist
• Adding extra words like 'start' before ruby
• Forgetting to include the .rb extension

3. Given a file greet.rb with the following content:

puts "Hello, Ruby!"

What will be the output when you run ruby greet.rb in the terminal?

medium

A. Hello, Ruby!

B. puts "Hello, Ruby!"

C. SyntaxError

D. No output

Solution

1. Step 1: Understand the Ruby code

   The code uses puts to print the string "Hello, Ruby!" to the terminal.

2. Step 2: Predict the output of running the script

   Running ruby greet.rb executes the code and prints the string.

3. Final Answer:

   Hello, Ruby! -> Option A

4. Quick Check:

   puts prints string output = C [OK]

Hint: puts prints text exactly when script runs [OK]

Common Mistakes:

• Thinking puts prints the code itself
• Expecting no output from puts
• Confusing syntax errors with correct code

4. You try to run a Ruby script with ruby myscript.rb but get an error: ruby: command not found. What is the most likely cause?

medium

A. The script file myscript.rb has a syntax error.

B. Ruby is not installed or not in your system's PATH.

C. You forgot to save the script file.

D. You need to add ./ before the filename.

Solution

1. Step 1: Analyze the error message

   The error ruby: command not found means the terminal cannot find the ruby program.

2. Step 2: Identify the cause

   This usually means Ruby is not installed or its location is not in the system PATH environment variable.

3. Final Answer:

   Ruby is not installed or not in your system's PATH. -> Option B

4. Quick Check:

   Command not found means Ruby missing or PATH issue [OK]

Hint: Command not found means Ruby missing or PATH issue [OK]

Common Mistakes:

• Assuming syntax error causes command not found
• Thinking file must be saved to fix this error
• Adding ./ before filename only works for executables, not ruby command

5. You have two Ruby scripts in the same folder: first.rb and second.rb. You want to run second.rb but accidentally type ruby first.rb. How can you avoid this mistake when running scripts?

hard

A. Use ruby run second.rb to specify the script.

B. Rename the files to have different extensions.

C. Always check your current folder and type the exact filename with extension.

D. Run scripts without typing the filename; Ruby will pick the right one.

Solution

1. Step 1: Understand the cause of the mistake

   Typing the wrong filename runs the wrong script because the command requires exact filenames.

2. Step 2: Find the best practice to avoid errors

   Always verify your current folder and type the exact filename with extension to run the correct script.

3. Final Answer:

   Always check your current folder and type the exact filename with extension. -> Option C

4. Quick Check:

   Exact filename avoids running wrong script [OK]

Hint: Double-check filename and folder before running script [OK]

Common Mistakes:

• Thinking Ruby auto-selects the right script
• Trying to run scripts without filenames
• Using incorrect commands like 'ruby run'