c('PL_thread

Documentation
- Reference manual
  - Multithreaded applications
    - Multithreaded mixed C and Prolog applications
      - A Prolog thread for each native thread (one-to-one)
        
        PL_thread_self()
        
        PL_unify_thread_id()
        
        PL_thread_attach_engine()
        
        PL_thread_destroy_engine()
        
        PL_thread_at_exit()
- Packages

Availability:C-language interface function

int PL_thread_self()

Returns the integer Prolog identifier of the engine or -1 if the calling thread has no Prolog engine. This function is also provided in the single-threaded version of SWI-Prolog, where it returns -2.