6.6.3 Hookable Standard Streams

The standard I/O streams (input, output, and error) are hookable, i.e. the streams can be redefined by the user by calling SP_set_user_stream_hook() and/or SP_set_user_stream_post_hook(). These hook functions must be called before SP_initialize() (see Initializing the Prolog Engine). In custom built systems, they may be called in the hook function SU_initialize(). See The Application Builder.