> For the complete documentation index, see [llms.txt](https://concorrencia101.leandronsp.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://concorrencia101.leandronsp.com/parte-ii-concorrencia-em-diferentes-linguagens/concorrencia-em-ruby/threads.md).

# Threads

Agora que entendemos como funciona o forking de processos, vamos explorar as **threads**. Threads são uma forma mais leve de concorrência, permitindo que múltiplas tarefas sejam executadas dentro do mesmo processo, compartilhando o mesmo espaço de memória.

Conforme explicado no módulo de C, conseguimos criar POSIX Threads através da chamada de função `pthread_create`. Na linguagem Ruby, conseguimos manipular kernel threads [através da classe Thread.](https://ruby-doc.org/core-3.0.0/Thread.html)

<figure><img src="/files/mIbCMIxb7flXRlCbORAu" alt="" width="563"><figcaption></figcaption></figure>

```ruby
# Função que será executada pela thread
def handle
  puts "Hello from thread!"
end

# Cria uma thread
thread = Thread.new do
  handle
end

puts "Hello from main thread!"

# Aguarda a thread terminar
thread.join
```

```
Hello from main thread!
Hello from thread!
```

*Simples, não?* Podíamos também passar qualquer código Ruby pra dentro do bloco da thread, não precisa ser necessariamente um método:

```ruby
# Cria uma thread
thread = Thread.new do
  puts "Hello from thread!"
end

puts "Hello from main thread!"

# Aguarda a thread terminar
thread.join
```

## Um exemplo mais robusto

Agora vamos fazer um exemplo mais complexo com threads, assim como fizemos com forking de processos:

```ruby
def handle(thread_id)
  puts "Thread #{thread_id} is running..."
  sleep(2) # Simula uma tarefa que leva 2 segundos
  puts "Thread #{thread_id} is finished."
end

threads = []

# Criação das threads
3.times do |i|
  threads << Thread.new(i + 1) do |thread_id|
    handle(thread_id) # Passa o ID da thread como argumento
  end
end

# Aguarda todas as threads finalizarem
threads.each_with_index do |thread, i|
  thread.join
  puts "Thread #{i + 1} has been finished."
end

puts "All threads are finished."
```

```
Thread 1 is running...
Thread 2 is running...
Thread 3 is running...
Thread 1 is finished.
Thread 3 is finished.
Thread 2 is finished.
Thread 1 has been finished.
Thread 2 has been finished.
Thread 3 has been finished.
All threads are finished.
```

*Ruby dispensa comentários, não?*

***

Vamos agora ver como Ruby resolve problemas de **race condition.**