Thread creation and execution in Ruby

Introduction

Threads let your program do many things at the same time. This helps make your program faster and more responsive.

When you want to download multiple files at once.

When you want to run a timer while your program waits for user input.

When you want to do background work without stopping the main program.

When you want to handle many tasks that can run independently.

When you want to keep your program responsive during long operations.

Syntax

Ruby

thread = Thread.new do
  # code to run in the thread
end

thread.join  # wait for the thread to finish

The Thread.new method starts a new thread and runs the code inside the block.

Use thread.join to wait for the thread to finish before continuing.

Examples

This creates a thread that prints a message, then waits for it to finish.

Ruby

thread = Thread.new do
  puts "Hello from thread!"
end

thread.join

This creates two threads that print messages independently, then waits for both.

Ruby

thread1 = Thread.new { puts "First thread" }
thread2 = Thread.new { puts "Second thread" }

thread1.join
thread2.join

This thread counts from 0 to 2 with a 1-second pause between each count.

Ruby

thread = Thread.new do
  3.times do |i|
    puts "Count: #{i}"
    sleep(1)
  end
end

thread.join

Sample Program

This program starts a thread that counts to 4 with pauses. Meanwhile, the main program prints a message and waits for the thread to finish before printing the last message.

Ruby

thread = Thread.new do
  5.times do |i|
    puts "Thread counting: #{i}"
    sleep(0.5)
  end
end

puts "Main program continues"

thread.join
puts "Thread finished"

Important Notes

Threads share the same memory space, so be careful when changing shared data.

Use sleep to pause a thread without stopping the whole program.

Always join threads if you want to wait for them to finish before ending the program.

Summary

Threads let your program do many things at once.

Create threads with Thread.new and run code inside a block.

Use join to wait for threads to finish.