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Date: Thu, 29 Aug 1996 16:50:35 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199608290650.QAA31554@godzilla.zeta.org.au>
To: hackers@FreeBSD.org, rnordier@iafrica.com
Subject: Re: Determining disk type & size
Sender: owner-hackers@FreeBSD.org
X-Loop: FreeBSD.org
Precedence: bulk

>Could anyone tell me if there is a quick and easy way to do the
>following:

>For a given (block special) device, determine whether it represents
>
>   (1) a floppy disk
>   (2) a hard disk slice that contains a filesystem (probably not ufs)
>   (3) anything else (not interested, but could be cdrom, tape, etc)

>and, given this info, the size (in bytes or 512-byte sectors) of the
>disk or slice itself.  For example:
>
>   device       blocks
>   ----------   ------
>   /dev/fd1       2400
>   /dev/wd0s1    65457
>   /dev/wd0     (error)

No easy way.  Perhaps no way.

>./fdtest /dev/fd0
>sectors per cylinder: 158 [<-- 30 expected]

>   if (ioctl(fd, DIOCGDINFO, &dl) == -1)
>      err(1, argv[1]);
>   printf("sectors per cylinder: %lu\n", dl.d_secpercyl);

DIOCGDINFO for floppies just returns whatever happens to be in the label
area on the disk (*).  The label is garbage unless the disk actually has
a label.  There is no way to tell from the ioctl() return value whether
the label is garbage.

Bruce