in reply to Re: get the size of a LARGE file
in thread get the size of a LARGE file

Just one thing I forgot: st_blksize is not the size of one block, but the preferred I/O block size for the file system.

So you have to get the size of one block somewhere else.

--Björn

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Re: Re: Re: get the size of a LARGE file
by TheHobbit (Pilgrim) on Apr 25, 2002 at 10:20 UTC

    Hi,
    beside the fact that st_blksize is not the blocksize but only the system preferred bloksize, there is a much more upsetting problem. Multiplying the number of blocks by the size of one block does not give you the size of the file. See the following example, where the file a just contains 4 carcters. 

    @a = stat "a";
print "Real size = $a[7]\n";
print "blocksize * blocknum = ",$a[11]*$a[12],"\n";

    [download]
    prints 
    size = 4
blocksize * blocknum =  32768

    [download]
    and everyone will agree that a file size function which returns 32768 instead of 4 is quite wrong.

    Of course, one my object that 32768 is the space that the file is taking up on your HD, but this is another story, as Kipling would have said.

    Cheers
    Leo TheHobbit
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      Multiplying the number of blocks by the size of one block does not give you the size of the file.

      When the filesize is up in the gigabytes, the bytes lost by multiplying file blocks by disk blocksize are down in the noise. Given the uses that file sizes of this magnitude are put to (e.g., how much tape is needed to back this file up; how long will it take to move this file from A to B, and how much disk space will it need when it gets there), losing a few bytes doesn't matter.

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