status.i4.v = fm_get_filename_c(vun.i2.v, file_name.i1a.r)

	This routine will return the file name for the file referenced
	by the virtual unit ID "vun".

	vun		virtual unit number of file
	file_name	returned null terminated file name

	This function returns ACNET status values as follows:

	OK			success
	CBS_NOTOPN		VUN is not in use

	This function requires the following include files:

	cbslib_h, acnet_errors_h

	Related functions:

	fm_open(_c), fm_open_io(_c), fm_open_read(_c), fm_open_write(_c),

	C/C++ usage:

	char	file_name[256];
	short	vun;
	int	status;

	status = fm_get_filename_c(vun,file_name);