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Predicate current_stream/3
Availability::- use_module(library(quintus)).(can be autoloaded)
Source[deprecated]current_stream(?Object, ?Mode, ?Stream)
The predicate current_stream/3 is used to access the status of a stream as well as to generate all open streams. Object is the name of the file opened if the stream refers to an open file, an integer file descriptor if the stream encapsulates an operating system stream, or the atom [] if the stream refers to some other object. Mode is one of read or write.

This predicate is deprecated. New code should use the ISO predicate stream_property/2.

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Jan Wielemaker said (2016-12-15T14:11:53):0 upvotes 0 0 downvotes
Picture of user Jan Wielemaker.

You do not need current_stream/3 for that:

?- stream_property(X, file_no(2)).
X = <stream>(0x7fe319340030).
Douglas Miles said (2016-12-15T11:44:32):0 upvotes 0 0 downvotes
Picture of user Douglas Miles.

One awesome feature of this predicate is..

If user_error is somehow redirected. from set_prolog_IO/3

 ?- current_stream(2,write,ConsoleErr),format(ConsoleErr,'hi~n',[]).

Will find the real console error stream