Date: Thu, 22 Jun 2006 20:33:45 -0500 From: Eric Anderson <anderson@centtech.com> To: Dan Nelson <dnelson@allantgroup.com> Cc: freebsd-hackers@freebsd.org, Mike Meyer <mwm-keyword-freebsdhackers2.e313df@mired.org>, Andrew <andrew.chace@gmail.com> Subject: Re: Coding question: finding the size of a block device Message-ID: <449B44F9.70006@centtech.com> In-Reply-To: <20060622220127.GE74589@dan.emsphone.com> References: <1151008839.2360.30.camel@LatitudeFC5.network> <17563.3550.496244.953904@bhuda.mired.org> <20060622220127.GE74589@dan.emsphone.com>
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Dan Nelson wrote:
> In the last episode (Jun 22), Mike Meyer said:
>> In <1151008839.2360.30.camel@LatitudeFC5.network>, Andrew <andrew.chace@gmail.com> typed:
>>> So I guess my question is: is there a POSIX compatible function that
>>> will allow me to check the size of a given block device?
>> I'd be surprised - POSIX doesn't seem to deal with block devices at all.
>>
>> Checking the sources to df, it uses statfs to get the
>> information. Linux appears to have it as well, so it may be portable.
>
> statfs only works on mounted filesystems, not arbitrary block devices.
>
> /usr/sbin/diskinfo uses ioctl(fd, DIOCGMEDIASIZE, &mediasize), where
> mediasize is an off_t.
>
Maybe something like this?
-----------
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <stdint.h>
#include <sys/disk.h>
int main(int argc, char **argv)
{
int devfd, error;
if (argc != 2) {
fprintf(stderr, "Need to specify device\n");
exit(1);
}
devfd = open(argv[1], O_RDONLY);
if (devfd < 0) {
fprintf(stderr, "Failed to open device\n");
exit(1);
}
error = getdiskinfo(devfd);
return (0);
}
int
getdiskinfo (int fd)
{
int error;
off_t mediasize;
u_int sectorsize;
error = ioctl(fd, DIOCGMEDIASIZE, &mediasize);
if (error)
printf("ioctl(DIOCGMEDIASIZE) failed, probably not a disk.");
error = ioctl(fd, DIOCGSECTORSIZE, §orsize);
if (error)
printf("DIOCGSECTORSIZE failed, probably not a disk.");
printf("Sector size: %d \n", sectorsize);
printf("Media size: %jd\n", (intmax_t)mediasize);
printf("Media: %jd sectors\n", (intmax_t)mediasize/sectorsize);
return(error);
}
---------------
--
------------------------------------------------------------------------
Eric Anderson Sr. Systems Administrator Centaur Technology
Anything that works is better than anything that doesn't.
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