SWI-Prolog -- thread_get

Documentation
- Reference manual
  - Multithreaded applications
    - Thread communication
      - Message queues
        
        thread_send_message/2
        
        thread_send_message/3
        
        thread_get_message/1
        
        thread_peek_message/1
        
        message_queue_create/1
        
        message_queue_create/2
        
        message_queue_destroy/1
        
        thread_get_message/2
        
        thread_get_message/3
        
        thread_peek_message/2
        
        message_queue_property/2
- Packages

Availability:built-in

thread_get_message(?Term)

Examines the thread message queue and if necessary blocks execution until a term that unifies to Term arrives in the queue. After a term from the queue has been unified to Term, the term is deleted from the queue.

Please note that non-unifying messages remain in the queue. After the following has been executed, thread 1 has the term b(gnu) in its queue and continues execution using A = gnat.

   <thread 1>
   thread_get_message(a(A)),

   <thread 2>
   thread_send_message(Thread_1, b(gnu)),
   thread_send_message(Thread_1, a(gnat)),