HGetVol
HGetVol Obtain default volume/directory name and reference
#include <Files.h> File Manager (PBxxx)
OSErr HGetVol( volName, vRefNum, dirID );
StringPtr volName; volume name (maximum length of 28 characters)
short * vRefNum; volume or working directory reference number
long *dirID; volume's directory ID
returns Error Code; 0=no error
Use HGetVol to get the vRefNum and dirID of the current default volume or
directory. It is similar to PBGetVol, except it uses refNums and dirID's
instead of a ParmBlkPtr.
Returns: an operating system Error Code. It will be one of:
noErr (0) No error
nsvErr (-35) No such volume
paramErr (-50) No default volume

Notes: The ioNamePtr field can be NIL to ignore the name. Otherwise, it should
point to a 28-byte buffer to hold the maximum 27-character name of the
default volume. Note that this does NOT return a multiple-name directory
name, even when a previous SetVol set the default to a working directory.