Re: Coding question: finding the size of a block device

[Eric Anderson]

Dan Nelson wrote:

In the last episode (Jun 22), Mike Meyer said:

In <[EMAIL PROTECTED]>, Andrew <[EMAIL PROTECTED]> 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, &sectorsize);
        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.
------------------------------------------------------------------------
_______________________________________________
freebsd-hackers@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
To unsubscribe, send any mail to "[EMAIL PROTECTED]"