SWI-Prolog -- library(settings)

convert_setting_text/3	Converts from textual form to Prolog Value.
current_setting/1	True if Setting is a currently defined setting.
env/2	Evaluate environment variables on behalf of arithmetic expressions.
env/3	Evaluate environment variables on behalf of arithmetic expressions.
list_settings/0	List settings to =current_output=.
list_settings/1	List settings to =current_output=.
load_settings/1	Load local settings from File.
load_settings/2	Load local settings from File.
restore_setting/1	Restore the value of setting Name to its default.
save_settings/0	Save modified settings to File.
save_settings/1	Save modified settings to File.
set_setting/2	Change a setting.
set_setting_default/2	Change the default for a setting.
setting/2	True when Name is a currently defined setting with Value.
setting/4	Define a setting.
setting_property/2	Query currently defined settings.