The only way that would work across those two systems is to open the file, read all the records and sum the size. If it is a formatted file and you don't want to count record separators (Windows), then something like this would work (I think)
SIZE=0
DO
READ (1,'(Q)',IOSTAT=IOS) RSIZE
IF (IOS /= 0) EXIT
SIZE = SIZE + RSIZE
END DO
Q is an extension that causes the number of unread bytes remaining in the record to be assigned to the next variable in the I/O list. It is supported by DEC/Compaq Fortran on VMS and by Intel Fortran.
If it is an unformatted file, this is harder.
An alternative is to write a utility routine to get the file size and use conditional compilation in that routine to use an OS-specific method.
