VMS Help CC, Run-time functions, decc$set_child_standard_streams  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  For a child spawned by a function from the exec family of
  functions, associates specified file descriptors with a child's
  standard streams:  stdin, stdout, and stderr.

  Syntax:

       #include <unistd.h>

       int decc$set_child_standard_streams(int fd1, int fd2,
       int fd3);