[det]dup(+FromStream,
+ToStream)dup2(), copying the underlying
filedescriptor and thus making both streams point to the same underlying
object. This is normally used together with fork/1
and pipe/2 to talk to an external
program that is designed to communicate using standard I/O.
Both FromStream and ToStream either refer to a
Prolog stream or an integer descriptor number to refer directly to OS
descriptors. See also demo/pipe.pl in the
source-distribution of this package.