BSD 4.3 F77 fortran query

[Michael Cohen]

Does anybody know an easy way to popen a stream which can be passed
to Fortran and associated with a fortran Unit,.  This is for a version
of BSD4.3 F77.  What was already tried was a fortran open followed
by a dup2 using the fortran unit as a file descriptor as passed to C.
This doesn't seem to work.  If anybody knows how to do this or
has the location of a routine which works this would be of interest.