@spiceErrorCheck<EOL>def fn2lun(fname):
fnameP    = stypes.stringToCharP(fname)<EOL>unit_out  = ctypes.c_int()<EOL>fname_len = ctypes.c_int(len(fname)+<NUM_LIT:1>)<EOL>libspice.fn2lun_(fnameP,ctypes.byref(unit_out),fname_len)<EOL>return unit_out.value<EOL>
Internal undocumented command for mapping name of open file to
its FORTRAN (F2C) logical unit.

https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/spicelib/fn2lun.html

:param fname: name of the file to be mapped to its logical unit.
:type fname: str
:return: the FORTRAN (F2C) logical unit associated with the filename.
:rtype: int