SWI-Prolog -- debug_print

prolog:debug_print_hook(+Topic, +Format, +Args) is semidet[multifile, library(syslog)]: Integration of debug/3 with the syslog facility. If syslog is enabled, debug/3 is re-routed to use the syslog facilities. If the topic of the debug message matches one of the sylog priority values (see syslog/2), the message is sent with the corresponding syslog priority. Otherwise it it sent with the debug priority.