Path: utzoo!attcan!uunet!samsung!usc!wuarchive!udel!rochester!cornell!calvin.spp.cornell.edu!richard
From: richard@calvin.spp.cornell.edu (Richard Brittain - VOS hacker)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Number of drives on system, how do you find out the ...
Summary: Use the ioctl for fixed/removable media
Keywords: MS-DOS, drives
Message-ID: <1990Oct20.021736.11447@calvin.spp.cornell.edu>
Date: 20 Oct 90 02:17:36 GMT
References: <1085@duteca4.UUCP>
Organization: Cornell Space Plasma Physics
Lines: 23

In article <1085@duteca4.UUCP> kooijman@duteca (Richard Kooijman) writes:
>How do you find out what the actual number of drives is on a MS-DOS computer?
>I have programmed a utility like NCD. It searches all disks on the computer
>to build a database of directories. Later this database can be used to switch
>quickly to another directory.

The setdisk() function returns the number corresponding to the LASTDRIVE=
line in config.sys, which defaults to 5 (A-E) if not given.  If your 
definition of "drive" means any logical/physical/virtual/networked/subst/joined
entity that can legally be addressed as a block device, then I recommend
you test all the drives up to the LASTDRIVE= using the ioctl call for
"test for fixed or removable media".  This gives an error code for 
drives which are bogus, and a valid return for all other (real, networked,
virtual, RAM, subst, etc.).  Best of all though, it makes no disc access
to do this, so it is very fast and never trips the critical error interrupt.
I don't have my references handy, but it should be listed in any of the
standard books - it's even documented!.

-- 
Richard Brittain,                   School of Elect. Eng.,  Upson Hall   
                                    Cornell University, Ithaca, NY 14853
ARPA: richard@calvin.spp.cornell.edu	
UUCP: {uunet,uw-beaver,rochester,cmcl2}!cornell!calvin!richard