SWI-Prolog -- sig_pending/1

Documentation
- Reference manual
  - Multithreaded applications
    - Thread communication
      - Signalling threads
        
        thread_signal/2
        
        sig_pending/1
        
        sig_remove/2
        
        sig_block/1
        
        sig_unblock/1
        
        sig_atomic/1
- Packages

Availability:built-in

[det]sig_pending(-List)

True when List contains all signals submitted using thread_signal/2 that are not yet processed. This includes signals blocked by sig_block/1.