Re: [vox-tech] files with holes in them

[jdnewmil@dcn.davis.caMAPS.us]

On Fri, 17 Nov 2000, Peter Jay Salzman wrote:

> i was playing around with creating files with holes in them:
> 
>       % ls -l holy_file
>       -rw-------    1 p        p        10000003 Nov 17 19:59 holy_file
> 
>       % du -k holy_file
>       24      holy_file
> 
> the program i wrote to generate this file looks more or less like:
> 
>       if((fd = open("holy_file", O_WRONLY|O_CREAT)) < 0)
>               exit(0);
> 
>       write(fd, string1, strlen(string1));
>       lseek(fd, 99999, SEEK_SET);
>       write(fd, string2, strlen(string2));
> 
> ls gets its info from stat.  i did an strace on du, and it also calls stat.
> i'm curious about the discrepency in file size.  does anyone know why the
> two programs report different file sizes?

Because by design du looks at allocated disk space, and ls looks at the
recorded file size.  From "man stat", I gather the former comes from
st_blocks and the latter comes from st_size.

But you knew this already... or you wouldn't have been playing with holey
files... right?

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