unix:sysconf/1

sysconf(+Conf) is semidet: Access system configuration. See sysconf(1) for details. Conf is a term Config(Value), where Value is always an integer. Config is the sysconf() name after removing =_SC_= and conversion to lowercase. Currently support the following configuration info: arg_max, child_max, clk_tck, open_max, pagesize, phys_pages, avphys_pages, nprocessors_conf and nprocessors_onln. Note that not all values may be supported on all operating systems.