Messages in this thread | | | Date | Sat, 12 Nov 2005 08:41:36 -0500 | From | Bill Davidsen <> | Subject | Re: Compatible fstat() |
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Parag Warudkar wrote:
> > On Nov 8, 2005, at 5:57 PM, Bill Davidsen wrote: > >> Parag Warudkar wrote: >> >>> On Nov 8, 2005, at 2:39 PM, Bob Copeland wrote: >>> >>>> Isn't this just because the device size is > 2**32? What if you >>>> use fseeko(3) >>>> and #define _FILE_OFFSET_BITS 64? >>>> >>> Yep. I got it to return the correct hard disk size (17Gb) using >>> lseek64 and >>> #define _LARGEFILE64_SOURCE >>> #define _FILE_OFFSET_BITS 64 >>> Here is what I did >>> ------------------------------------------------- >>> #define _LARGEFILE64_SOURCE >>> #define _FILE_OFFSET_BITS 64 >>> #include <stdio.h> >>> #include <unistd.h> >>> #include <fcntl.h> >>> int main() >>> { >>> int f; >>> off64_t off=0; >> >> Why is this initialized? >> >>> f = open("/dev/hda", O_RDONLY ); >>> if(f <= 0){ >>> perror("open"); >>> exit(0); >>> } >>> off = lseek64(f, 0, SEEK_SET); >> >> Why do this? it always returns zero. >> >>> off = lseek64(f, 0, SEEK_END); >>> perror("llseek"); >>> printf ("Size %lld\n", off); >>> close(f); >>> return 0; >>> } >> >> RETURN VALUE >> Upon successful completion, lseek returns the resulting offset >> location as measured in bytes from the beginning of the file. >> Otherwise, a value of (off_t)-1 is returned and errno is >> set to indicate the error. >> > > You took it a little too seriously! It was from the scribble-and- > shuffle-till-it-works department ;) Sole purpose was to figure out a > way to print the disk size from the device - some how that is! > > But thanks for pointing out anyway - it doesn't hurt to be correct no > matter what the purpose is.
You could look at how blockdev does it, the --getss (sector size) and --getsize (size in sectors) seem to work, based on trying it on a total of two machines ;-) Even gives correct size for software RAID arrays!
-- bill davidsen <davidsen@tmr.com> CTO TMR Associates, Inc Doing interesting things with small computers since 1979
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