SWI-Prolog -- prolog_alert

Availability:built-in

prolog_alert_signal(?Old, +New)

Query or set the signal used to unblock blocking system calls on Unix(-like) systems and process pending Prolog signals. The default is SIGUSR2. See also --sigalert. New can be a signal name or number. See on_signal/3 for how the Prolog signal name is defined. The Old argument is unified to the signal name if known and the number otherwise. Notably the value 0 (zero) indicates that the system does not use an alarm signal. On POSIX systems, this implies that system calls are not interrupted by thread_signal/2.

This predicate is only defined on systems where the alert signal mechanism is used.